UsetheselinkstorapidlyreviewthedocumentTableofContents

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Filed Pursuant to Rule 424(b)(7) File No. 333-210226

The information in this preliminary prospectus supplement is not complete and may be changed. A registration statement relating to the securities hasbecome effective under the Securities Act of 1933, as amended. This preliminary prospectus supplement and the accompanying prospectus are not anoffer to sell these securities, and we are not soliciting an offer to buy these securities, in any jurisdiction where the offer or sale is not permitted.

Subject to completion, dated September 19, 2016

Prospectus Supplement to Prospectus dated March 15, 2016

TRINSEO S.A.10,669,567 Ordinary Shares

Thesellingshareholdernamedinthisprospectussupplementisoffering10,669,567ofourordinaryshares.Wewillnotreceiveanyproceedsfromthesaleofourordinarysharesbythesellingshareholder.

OurordinarysharesarelistedontheNewYorkStockExchangeunderthesymbol"TSE."OnSeptember19,2016,thelastsalepriceofourordinarysharesasreportedontheNewYorkStockExchangewas$55.76perordinaryshare.

Investing in our ordinary shares involves substantial risk. Please read "Risk Factors" beginning on page S-8 of thisprospectus supplement and on page 3 of the accompanying base prospectus.

NeithertheSecuritiesandExchangeCommissionnoranyotherregulatorybodyhasapprovedordisapprovedofthesesecuritiesorpassedupontheaccuracyoradequacyofthisprospectussupplementortheaccompanyingprospectus.Anyrepresentationtothecontraryisacriminaloffense.

Theunderwriterhasagreedtopurchaseourordinarysharesfromthesellingshareholderatapriceof$pershare,whichwillresultinapproximately$ofproceedstothesellingshareholderbeforeexpenses.TheunderwritermayoffertheordinarysharesfromtimetotimeforsaleinoneormoretransactionsontheNewYorkStockExchange,intheover-the-countermarket,throughnegotiatedtransactionsorotherwiseatmarketpricesprevailingatthetimeofsale,atpricesrelatedtoprevailingmarketpricesoratnegotiatedprices,subjecttoreceiptandacceptancebyitandsubjecttoitsrighttorejectanyorderinwholeorinpart.Wehaveagreedtoreimbursetheunderwriterforcertainexpensesinconnectionwiththisoffering.See"Underwriting."

TheunderwriterexpectstodeliverthesharesagainstpaymentinNewYork,NewYorkonorabout,2016.

Morgan Stanley

Thedateofthisprospectussupplementis,2016

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Prospectus

Wehavenotauthorizedanyonetoprovideanyinformationortomakeanyrepresentationsotherthanthosecontainedinorincorporatedbyreferenceintothisprospectussupplement,theaccompanyingprospectusorinanyfreewritingprospectuseswehaveprepared.Wetakenoresponsibilityfor,andcanprovidenoassuranceastothereliabilityof,anyotherinformationthatothersmaygiveyou.Thisprospectussupplementandtheaccompanyingprospectusareanoffertosellonlythesharesofferedhereby,butonlyundercircumstancesandinjurisdictionswhereitislawfultodoso.Theinformationcontainedinthisprospectussupplementandtheaccompanyingprospectusiscurrentonlyasofthedateoftheapplicabledocument.

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ABOUTTHISPROSPECTUSSUPPLEMENT S-iiNON-GAAPFINANCIALMEASURES S-iiPROSPECTUSSUPPLEMENTSUMMARY S-1RISKFACTORS S-8CAUTIONARYNOTEREGARDINGFORWARD-LOOKINGSTATEMENTS S-11USEOFPROCEEDS S-13MARKETPRICEOFOURORDINARYSHARES S-14DIVIDENDPOLICY S-15DESCRIPTIONOFSHARECAPITAL S-16MATERIALUNITEDSTATESFEDERALINCOMEANDLUXEMBOURGTAXCONSIDERATIONS S-24SELLINGSHAREHOLDER S-34UNDERWRITING S-35LEGALMATTERS S-40EXPERTS S-40WHEREYOUCANFINDMOREINFORMATION S-40INCORPORATIONOFCERTAININFORMATIONBYREFERENCE S-40

AboutThisProspectus 1AboutTrinseoS.A. 2RiskFactors 3CautionaryNoteRegardingForward-LookingStatements 4UseofProceeds 6SellingShareholder 6PlanofDistribution 7LegalMatters 9Experts 9WhereYouCanFindMoreInformation 9IncorporationofCertainInformationbyReference 9

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ABOUT THIS PROSPECTUS SUPPLEMENT

Unlessotherwiseindicatedorthecontextotherwiserequires,theterms"Trinseo,""we,""us,""our,""ourCompany,"and"ourbusiness"refertoTrinseoS.A.togetherwithitsconsolidatedsubsidiaries.Priortoourformation,ourbusinesseswerewholly-ownedbyTheDowChemicalCompany,whichwerefertoas"Dow."Werefertoourpredecessorbusinessesas"theStyronbusiness."OnJune17,2010,investmentfundsadvisedormanagedbyBainCapitalPrivateEquity,LPacquiredtheStyronbusiness,andDowEuropeHoldingB.V.retainedanownershipinterestintheStyronbusinessthroughanindirectownershipinterestinus.Referencesto"sellingshareholder"and"Parent"refertoBainCapitalEverestManagerHoldingSCA,whoissellingsharespursuanttothisprospectussupplement.

Thisdocumentisintwoparts.Thefirstpartisthisprospectussupplement,whichdescribesthespecifictermsofthisofferingofordinarysharesandcertainothermattersrelatingtous,ourbusinessandprospects.Thesecondpart,theaccompanyingprospectus,containscertainotherinformation.

Theinformationcontainedinthisprospectussupplementmayadd,updateorchangeinformationcontainedintheaccompanyingprospectusorindocumentsthatwefileorhavefiledwiththeSecuritiesandExchangeCommission(the"SEC").Totheextenttheinformationcontainedinthisprospectussupplementdiffersorvariesfromtheinformationcontainedintheaccompanyingprospectusordocumentsincorporatedbyreferencefiledbeforethedateofthisprospectussupplement,theinformationinthisprospectussupplementwillsupersedesuchinformation.

NON-GAAP FINANCIAL MEASURES

WerefertothetermsEBITDA,AdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluationinthisprospectussupplement,theaccompanyingprospectusanddocumentsincorporatedbyreferencehereinandtherein.ThesearesupplementalfinancialmeasuresthatarenotpreparedinaccordancewithU.S.GenerallyAcceptedAccountingPrinciples("GAAP").Anyanalysisofnon-GAAPfinancialmeasuresshouldbeusedonlyinconjunctionwithresultspresentedinaccordancewithGAAP.

Seenote4tothesectiontitled"ProspectusSupplementSummary—SummaryHistoricalFinancialandOperatingData"foradescriptionofthecalculationofEBITDA,AdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluation,includingthereasonsthatwebelievethisinformationisusefultomanagementandwhyitmaybeusefultoinvestors,andareconciliationofEBITDA,AdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluationtothemostcloselycomparablefinancialmeasurecalculatedinaccordancewithGAAP.OurmeasurementsofEBITDA,AdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluationmaynotbecomparabletothoseofothercompanies.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights information appearing elsewhere or incorporated by reference in this prospectus supplement and the accompanyingprospectus. This summary is not complete and does not contain all of the information that you should consider before investing in our ordinary shares. Youshould carefully read this entire prospectus supplement, the accompanying prospectus and the financial data and related notes and other informationincorporated by reference in this prospectus supplement and the accompanying prospectus before deciding whether to invest in our ordinary shares.

Our Company

Wearealeadingglobalmaterialscompanyengagedinthemanufactureandmarketingofsyntheticrubber,latex,andplastics,includingvariousspecialtyandtechnologicallydifferentiatedproducts.Webelievethatgrowthinoverallconsumerspendingandconstructionactivity,increaseddemandintheautomotiveindustryforhigherfuelefficiencyandlighter-weightmaterials,andimprovinglivingstandardsinemergingmarketswillresultingrowthintheglobalmarketsinwhichwecompete.Inaddition,webelieveourincreasingbusinesspresenceindevelopingregionssuchasChina,SoutheastAsia,andEasternEuropefurtherenhancesourprospects.

Wedevelopsyntheticrubber,latexandplasticsproductsthatareincorporatedintoawiderangeofourcustomers'productsthroughouttheworld,includingtiresandotherproductsforautomotiveapplications,carpetandartificialturfbacking,coatedpaperandpackagingboard,foodpackaging,appliances,medicaldevices,consumerelectronicsandconstructionapplications,amongothers.Weseektoregularlydevelopnewandimprovedproductsandprocesses,supportedbyourintellectualpropertyportfolio,designedtoenhanceourcustomers'productofferings.Wehavelong-standingrelationshipswithadiversebaseofglobalcustomers,manyofwhomareleadersintheirmarketsandrelyonusforformulation,technologicaldifferentiation,andcompoundingexpertisetofindsustainablesolutionsfortheirbusinesses.Manyofourproductsrepresentonlyasmallportionofafinishedproduct'sproductioncosts,butprovidecriticalfunctionalitytothefinishedproductandareoftenspecificallydevelopedtocustomerspecifications.Webelievetheseproducttraitsresultinsubstantialcustomerloyaltyforourproducts.

Wehavesignificantmanufacturingandproductionoperationsaroundtheworld,whichallowsustoserveourglobalcustomerbase.AsofDecember31,2015,ourproductionfacilitiesincluded34manufacturingplants(whichincludedatotalof80productionunits)at26sitesacross14countries,includingjointventuresandcontractmanufacturers.OurmanufacturinglocationsincludesitesinemergingmarketssuchasChinaandIndonesia.Additionally,asofDecember31,2015,weoperated11researchanddevelopment("R&D")facilitiesglobally,includingminiplants,developmentcentersandpilotcoaters,whichwebelievearecriticaltoourglobalpresenceandinnovationcapabilities.

Weareaglobalbusinesswithadiversegeographicrevenuemixandsignificantoperationsaroundtheworld.

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ForthesixmonthsendedJune30,2016,wegeneratednetsalesof$1,863.8million,netincomeof$172.6million,AdjustedEBITDAof$325.6millionandAdjustedEBITDAexcludinginventoryrevaluationof$322.4million.FortheyearendedDecember31,2015,wegeneratednetsalesof$3,971.9million,netincomeof$133.6million,AdjustedEBITDAof$492.0millionandAdjustedEBITDAexcludinginventoryrevaluationof$550.3million.AdditionalinformationregardingAdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluation,includingareconciliationofthesemetricstonetincome(loss),isincludedinnote4tothetable"—SummaryHistoricalFinancialandOperatingData."

Recent Developments

Share Repurchases

Duringthethirdquarterof2016,theCompanycompleteditsrepurchaseprogramannouncedonJune22,2016.Undertheprogram,theCompanypurchased1,759,194ordinarysharesfromitsshareholdersthroughacombinationofopenmarkettransactionsforanaggregatepurchaseamountofapproximately$100.0million.Theshareswererepurchasedataweighted-averagepricepershareof$56.68.

Corporate Information

Ourglobaloperatingcenterislocatedat1000ChesterbrookBoulevard,Suite300,Berwyn,Pennsylvania19312,andourtelephonenumberatthisaddressis(610)240-3200.Wemaintainawebsiteatwww.trinseo.com.Theinformationon,orthatcanbeaccessedthrough,ourwebsiteisnotpartofthisprospectussupplementortheaccompanyingprospectus,andyoushouldnotrelyonanysuchinformationinmakingthedecisionwhethertopurchaseourordinaryshares.

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The Offering

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Ordinarysharesofferedbythesellingshareholder

10,669,567ordinaryshares.

Ordinarysharesoutstandingafterthisoffering

45,145,431ordinaryshares,excludingtreasuryshares.

Useofproceeds

Wewillnotreceiveanyoftheproceedsfromthesaleofourordinarysharesbythesellingshareholder.

Dividendpolicy

OnJuly20,2016,wemadearepaymentofequityof$0.30perordinarysharetoourshareholdersofrecordasofthecloseofbusinessonJuly6,2016.Althoughweexpecttocontinuetomakequarterlycashdistributionstoourshareholdersasrepaymentsofequityordividends,anyfuturedeterminationtopaydividendsormakeotherdistributionstoourshareholderswillbeatthediscretionofourboardofdirectors.See"DividendPolicy."

RiskfactorsYoushouldreadcarefullytheinformationsetforthunder"RiskFactors"hereinandintheaccompanyingprospectusforadiscussionoffactorsthatyoushouldconsiderbeforedecidingtoinvestinourordinaryshares.

NewYorkStockExchangetradingsymbol

"TSE".

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Summary Historical Financial and Operating Data

Thefollowingtablesetsforthoursummaryhistoricalfinancialandoperatingdataandotherinformationasofthedatesandfortheperiodsindicated.ThehistoricalresultsofoperationsforthethreeandsixmonthperiodsendedJune30,2016and2015,andthehistoricalbalancesheetdataasofJune30,2016presentedbelowwerederivedfromourunauditedcondensedconsolidatedfinancialstatementsandtherelatednotestheretoincorporatedbyreferenceintothisprospectussupplement.ThehistoricalresultsofoperationsdatafortheyearsendedDecember31,2015,2014,and2013,andthehistoricalbalancesheetdataasofDecember31,2015and2014presentedbelowwerederivedfromourauditedconsolidatedfinancialstatementsandtherelatednotestheretoincorporatedbyreferenceintothisprospectussupplement.ThehistoricalbalancesheetdataasofJune30,2015wasderivedfromourunauditedcondensedconsolidatedfinancialstatementsandtherelatednotestheretonotincorporatedbyreferenceintothisprospectussupplement.ThehistoricalbalancesheetdataasofDecember31,2013wasderivedfromourauditedconsolidatedfinancialstatementsandtherelatednotestheretonotincorporatedbyreferenceintothisprospectussupplement.ThedatainthefollowingtablerelatedtoEBITDA,AdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluationareunauditedforallperiodspresented.

Ourhistoricalresultsarenotnecessarilyindicativeoftheresultstobeexpectedforanyfutureperiods.

Thissummaryhistoricalfinancialandotherdatashouldbereadinconjunctionwiththedisclosuressetforthunder"Management'sDiscussionandAnalysisofFinancialConditionandResultsofOperations"andtheconsolidatedfinancialstatementsandtherelatednotesthereto,bothofwhichcanbefoundinourQuarterlyReportonForm10-QforthequarterendedJune30,2016andinourAnnualReportonForm10-KfortheyearendedDecember31,2015,eachofwhichisincorporatedbyreferenceherein.

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Three Months Ended

June 30, Six Months Ended

June 30, Year Ended December 31,

(in millions, except per share data) 2016 2015 2016 2015 2015 2014 2013 Statement of Operations Data: Netsales(1) $ 969.7 $ 1,028.7 $ 1,863.8 $ 2,046.9 $ 3,971.9 $ 5,128.0 $ 5,307.4Costofsales(1) 800.0 886.5 1,554.4 1,801.7 3,502.8 4,830.6 4,949.4Grossprofit 169.7 142.2 309.4 245.2 469.1 297.4 358.0Selling,generalandadministrativeexpenses 52.2 50.7 106.7 102.4 208.0 232.6 216.9Equityinearningsofunconsolidatedaffiliates 38.6 40.8 73.6 77.5 140.2 47.7 39.1

Operating income 156.1 132.3 276.3 220.3 401.3 112.5 180.2Interestexpense,net 18.8 25.6 37.7 54.5 93.2 124.9 132.0Lossonextinguishmentoflong-termdebt(2) — 95.2 — 95.2 95.2 7.4 20.7Otherexpense,net 12.9 3.2 15.5 6.7 9.1 27.8 27.9Income (loss) before income taxes 124.4 8.3 223.1 63.9 203.8 (47.6) (0.4)Provisionforincometaxes 28.6 7.5 50.5 25.4 70.2 19.7 21.8Net income (loss) $ 95.8 $ 0.8 $ 172.6 $ 38.5 $ 133.6 $ (67.3) $ (22.2)Weightedaverageshares—basic 47.0 48.8 47.8 48.8 48.8 43.5 37.3Netincome(loss)pershare—basic $ 2.04 $ 0.02 $ 3.61 $ 0.79 $ 2.74 $ (1.55) $ (0.60)Weightedaverageshares—diluted 47.9 48.9 48.6 48.9 49.0 43.5 37.3Netincome(loss)pershare—diluted $ 2.00 $ 0.02 $ 3.55 $ 0.79 $ 2.73 $ (1.55) $ (0.60)Repaymentofequitypershare $ 0.30 — $ 0.30 — — — —Other Financial Data: Depreciationandamortization $ 24.9 $ 21.7 $ 47.9 $ 44.2 $ 96.8 $ 103.7 $ 95.2Capitalexpenditures,netofsubsidy(3) 26.7 13.7 53.2 41.4 107.1 98.6 54.8EBITDA(4) 168.1 55.6 308.7 162.6 393.8 181.0 226.8AdjustedEBITDA(4) 182.4 151.3 325.6 260.1 492.0 261.6 277.9AdjustedEBITDAexcludinginventoryrevaluation(4) 169.5 121.9 322.4 272.9 550.3 326.0 318.3

Balance Sheet Data: Cashandcashequivalents $ 465.2 $ 231.1 $ 431.3 $ 220.8 $ 196.5Workingcapital(5) 928.8 741.1 839.8 748.7 810.2Totalassets(6) 2,362.6 2,289.1 2,258.9 2,356.1 2,574.8Debt(6) 1,188.3 1,221.2 1,182.1 1,202.2 1,336.4Totalliabilities(6) 1,899.2 2,001.2 1,869.9 2,035.3 2,231.6Totalshareholders'equity 463.4 287.9 389.0 320.9 343.2

(1) Netsalesandcostofsalesincreaseordecreasebasedonfluctuationsinrawmaterialprices.Consistentwithindustrypractice,andaspermittedunderagreementswithmanyofourcustomers,rawmaterialpricechangesaregenerallypassedthroughtocustomersbymeansofcorrespondingpricechanges.

(2) ForthethreeandsixmonthsendedJune30,2015andtheyearendedDecember31,2015,thelossonextinguishmentofdebtof$95.2millionrelatedtotheCompany'sdebtrefinancinginMay2015,andwascomprisedofbothacallpremiumandthewrite-offofunamortizeddeferredfinancingfees.FortheyearendedDecember31,2014,thelossonextinguishmentofdebtrelatedtotheJuly2014redemptionof$132.5millioninaggregateprincipalamountofthe2019SeniorNotes,usingaportionoftheproceedsfromourinitialpublicoffering.FortheyearendedDecember31,2013,thelossonextinguishmentofdebtrelatedtotheJanuary2013amendmentofour2018SeniorSecuredCreditFacilityandtherepaymentof$1,239.0millionofoutstandingTermLoans.NosuchchargeswererecordedforthethreeandsixmonthsendedJune30,2016.

(3) Representscapitalexpenditures,netofgovernmentsubsidiesreceivedforsolutionstyrene-butadienerubber,orSSBR,expansionof$2.2millionand$18.8millionfortheyearsendedDecember31,2015and2013,respectively.The$2.2millionofgovernmentsubsidiesreceivedin2015werereceivedduringthethreeandsixmonthsendedJune30,2015.NogovernmentsubsidieswerereceivedinthethreeandsixmonthsendedJune30,2016orintheyearendedDecember31,2014.FortheyearendedDecember31,2014,capitalexpendituresincludeapproximately$26.1millionforthereacquisitionofproductioncapacityrightsattheCompany'srubberproductionfacilityinSchkopau,Germany.

(4) WebelievethatthepresentationofAdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluationprovidesinvestorswithausefulanalyticalindicatorofourperformanceandofourabilitytoserviceourindebtedness.

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WedefineAdjustedEBITDAasincome(loss)fromcontinuingoperationsbeforeinterestexpense,net;incometaxprovision;depreciationandamortizationexpense;lossonextinguishmentoflong-termdebt;assetimpairmentcharges;advisoryfeespaidtoaffiliatesofourParent;gainsorlossesonthedispositionsofbusinessesandassets;restructuringandotheritems.Wedescribetheseothercostsinmoredetailbelow.

WepresentAdjustedEBITDAexcludinginventoryrevaluationinordertofacilitatethecomparabilityofresultsbyinvestorsfromperiodtoperiodbyadjustingcostofsalestoreflectthecostofrawmaterialduringtheperiod,whichisoftenreferredtoasthereplacementcostmethodofinventoryvaluation.Webelievethismeasureminimizestheimpactofrawmaterialpurchasepricevolatilityinevaluatingourperformance.OurapproachtocalculatinginventoryrevaluationisintendedtorepresentthedifferencebetweentheresultsundertheFIFOandthereplacementcostmethods.However,ourcalculationcoulddifferfromthereplacementcostmethodifthemonthlyrawmaterialstandardsaredifferentfromtheactualrawmaterialpricesduringthemonthandproductionandpurchasevolumesdifferfromsalesvolumesduringthemonth.Thesefactorscouldhaveasignificantimpactontheinventoryrevaluationcalculation.

TherearelimitationstousingfinancialmeasuressuchasAdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluation.TheseperformancemeasuresarenotintendedtorepresentcashflowfromoperationsasdefinedbyGAAPandshouldnotbeusedasalternativestonetincome(loss)asindicatorsofoperatingperformanceortocashflowasmeasuresofliquidity.OthercompaniesinourindustrymaydefineAdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluationdifferentlythanwedo.Asaresult,itmaybedifficulttousetheseorsimilarly-namedfinancialmeasuresthatothercompaniesmayuse,tocomparetheperformanceofthosecompaniestoourperformance.Wecompensatefortheselimitationsbyprovidingreconciliationsoftheseperformancemeasurestoournetincome(loss),whichisdeterminedinaccordancewithGAAP.

AdjustedEBITDAandAdjustedEBITDAexcludinginventoryrevaluationarecalculatedasfollowsforthethreeandsixmonthsendedJune30,2016and2015andfortheyearsendedDecember31,2015,2014,and2013,respectively:

Three Months Ended

June 30,

Six Months Ended

June 30,

Year Ended

December 31, (in millions) 2016 2015 2016 2015 2015 2014 2013 Net income (loss) $ 95.8 $ 0.8 $ 172.6 $ 38.5 $ 133.6 $ (67.3) $ (22.2)Interestexpense,net 18.8 25.6 37.7 54.5 93.2 124.9 132.0Provisionforincometaxes 28.6 7.5 50.5 25.4 70.2 19.7 21.8Depreciationandamortization 24.9 21.7 47.9 44.2 96.8 103.7 95.2EBITDA(a ) $ 168.1 $ 55.6 $ 308.7 $ 162.6 $ 393.8 $ 181.0 $ 226.8Lossonextinguishmentoflong-termdebt — 95.2 — 95.2 95.2 7.4 20.7Assetimpairmentchargesorwrite-offs(b) — — — — — — 9.9Netloss(gain)ondispositionofbusinessesandassets(c) 12.9 — 12.9 — — (0.6) 4.2

Restructuringandothercharges(d) 1.1 (0.1) 1.8 0.4 0.8 10.0 10.8Feespaidpursuanttoadvisoryagreement(e) — — — — — 25.4 4.7Otheritems(f) 0.3 0.6 2.2 1.9 2.2 38.4 0.8Adjusted EBITDA $ 182.4 $ 151.3 $ 325.6 $ 260.1 $ 492.0 $ 261.6 $ 277.9Inventoryrevaluation (12.9) (29.4) (3.2) 12.8 58.3 64.4 40.4Adjusted EBITDA excluding inventory

revaluation(g) $ 169.5 $ 121.9 $ 322.4 $ 272.9 $ 550.3 $ 326.0 $ 318.3

(a) WerefertoEBITDAinmakingoperatingdecisionsbecausewebelieveitprovidesmeaningfulsupplementalinformationregardingouroperationalperformance.OthercompaniesinourindustrymaydefineEBITDAdifferentlythanwedo.Asaresult,itmaybedifficulttouseEBITDA,orsimilarly-namedfinancialmeasuresthatothercompaniesmayuse,tocomparetheperformanceofthosecompaniestoourperformance.WecompensatefortheselimitationsbyprovidingreconciliationsofourEBITDAresultstoournetincome(loss),whichisdeterminedinaccordancewithGAAP.Seethe"SelectedSegmentInformation"inourQuarterlyReportonForm10-QforthequarterendedJune30,2016andourAnnualReportonForm10-KfortheyearendedDecember31,2015forfurtherdetailonEBITDAbyeachofourreportablesegments.

(b) Assetimpairmentchargesorwrite-offsfortheyearendedDecember31,2013relateprimarilytoa$9.2millionimpairmentchargeforfixedassetsatourpolycarbonatemanufacturingplantinStade,Germany.SeeNote7intheconsolidatedfinancialstatementsincludedinourAnnualReportonForm10-KfortheyearendedDecember31,2015forfurtherdiscussion.

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(c) DuringthethreeandsixmonthsendedJune30,2016,theCompanyrecordedanimpairmentchargefortheestimatedlossonsaleofourprimaryoperatingentityinBrazil,whichincludesbothlatexandautomotivebusinesses,ofapproximately$12.9million.SeeNote15inthecondensedconsolidatedfinancialstatementsinourQuarterlyReportonForm10-QforthequarterendedJune30,2016forfurtherdiscussion.Netloss(gain)ondispositionofbusinessesandassetsfortheyearsendedDecember31,2014and2013of$(0.6)millionand$4.2million,respectively,relatetothesaleoftheCompany'sexpandablepolystyrene,orEPS,business,whichclosedinSeptember2013,andforwhichacontingentgainof$0.6millionwasrecordedduringthefourthquarterof2014.SeeNote3intheconsolidatedfinancialstatementsinourAnnualReportonForm10-KfortheyearendedDecember31,2015forfurtherdiscussion.

(d) RestructuringandotherchargesforthethreeandsixmonthsendedJune30,2016relatetoemployeeterminationbenefitanddecommissioningchargesincurredinconnectionwiththeclosureofourAllyn'sPointlatexmanufacturingfacilityinGalesFerry,Connecticut,aswellasemploymentterminationbenefitchargesrelatedtotheexpectedeliminationofcertaincorporatefunctionspriortothesaleofourlatexandautomotivebusinessesinBrazil.RestructuringandotherchargesforthesixmonthsendedJune30,2015relateprimarilytothepolycarbonaterestructuringwithinourBasicPlastics&Feedstockssegment,forthereimbursementofdecommissioninganddemolitionchargestoDowinconnectionwiththeshutdownofitsFreeport,Texasfacility.SeeNote16tothecondensedconsolidatedfinancialstatementsincludedinourQuarterlyReportonForm10-QforthequarterendedJune30,2016forfurtherdiscussion.

RestructuringandotherchargesfortheyearendedDecember31,2015relateprimarilytothepolycarbonaterestructuringwithinourBasicPlastics&Feedstockssegmentnotedabove.RestructuringandotherchargesfortheyearsendedDecember31,2014and2013wereincurredprimarilyinconnectionwiththeshutdownofourlatexmanufacturingplantinAltona,AustraliaandtherestructuringwithinourBasicPlastics&Feedstockssegmentnotedabove.SeeNote20totheconsolidatedfinancialstatementsincludedinourAnnualReportonForm10-KfortheyearendedDecember31,2015forfurtherdiscussion.

NotethattheaccelerateddepreciationchargesincurredasapartoftheAllyn'sPointshutdown,andthe2014polycarbonaterestructuringwithinourBasicPlastics&Feedstockssegment,areincludedwithinthe"Depreciationandamortization"captionabove,andthereforearenotincludedasaseparateadjustmentwithinthiscaption.

(e) RepresentsfeespaidunderthetermsofouradvisoryagreementwithBainCapitalPrivateEquity,LP(the"AdvisoryAgreement").FortheyearendedDecember31,2014,thisincludesachargeof$23.3millionforfeesincurredinconnectionwiththeterminationoftheAdvisoryAgreement,pursuanttoitsterms,uponconsummationoftheCompany'sinitialpublicofferinginJune2014.SeeNote18totheconsolidatedfinancialstatementsincludedinourAnnualReportonForm10-KfortheyearendedDecember31,2015forfurtherdiscussion.

(f) OtheritemsforthethreeandsixmonthsendedJune30,2016relatetofeesincurredinconjunctionwiththeCompany'ssecondaryofferingscompletedinMay2016andMarch2016,respectively.SeeNote18inthecondensedconsolidatedfinancialstatementsinourQuarterlyReportonForm10-QforthequarterendedJune30,2016forfurtherdiscussion.OtheritemsforthethreeandsixmonthsendedJune30,2015andfortheyearsendedDecember31,2015and2014consistofcostsrelatedtotheprocessofchangingourcorporatenamefromStyrontoTrinseo.FortheyearendedDecember31,2014,thesecostsalsoincludeaone-time$32.5millionterminationpaymentmadetoDowinconnectionwiththeterminationofourLatexJVOptionAgreement.SeeNote18intheconsolidatedfinancialstatementsinourAnnualReportonForm10-KfortheyearendedDecember31,2015forfurtherdiscussion.

(g) SeethediscussionabovethistableforadescriptionofAdjustedEBITDAexcludinginventoryrevaluation.

(5) Workingcapitalisdefinedascurrentassetsminuscurrentliabilities.

(6) InApril2015,theFinancialAccountingStandardsBoard("FASB")issuedguidancethatrequiresdeferredfinancingfeesrelatedtoarecognizeddebtliabilitybepresentedonthebalancesheetasadirectreductionofthecarryingvalueofthatdebtliability,consistentwithdebtdiscounts.Therecognitionandmeasurementguidancefordeferredfinancingfeesarenotaffected.TheCompanyadoptedthisguidanceeffectiveJanuary1,2016.BalancesasofDecember31,2015presentedhereinhavebeenretrospectivelyadjustedtoreflectthisadoption,withresultingimpactstothecaptions"Totalassets"and"Totalliabilities,"consistentwithourQuarterlyReportonForm10-QforthequarterendedJune30,2016incorporatedbyreferenceherein.

Balancespresentedforallperiodswithinthe"Debt"captionabovereflectgrossdebtbalancesoutstandingateachperiodend,anddonotreflectareductionforthereclassificationofunamortizeddeferredfinancingfeesnotedabove.

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RISK FACTORS

An investment in our ordinary shares involves various risks. You should carefully consider the following risks and all of the other information contained inthis prospectus supplement and the accompanying prospectus before investing in our ordinary shares. In addition, you should read and consider the risk factorsassociated with our business included in the documents incorporated by reference in this prospectus supplement, including our Annual Report on Form 10-K forthe year ended December 31, 2015 and our Quarterly Report on Form 10-Q for the quarter ended June 30, 2016. See "Where You Can Find More Information."The risks described below and incorporated herein by reference are those which we believe are the material risks that we face. The trading price of our ordinaryshares could decline due to any of these risks, and you may lose all or part of your investment in our ordinary shares.

Risks Related to the Offering

Our share price could be extremely volatile, and, as a result, you may not be able to resell your ordinary shares at or above the price you paid for them.

SinceourinitialpublicofferinginJune2014,thepriceofanordinaryshare,asreportedontheNewYorkStockExchange,hasrangedfromalowof$11.92onNovember14,2014toahighof$60.02onAugust30,2016.Inaddition,thestockmarketingeneralhasbeenhighlyvolatile.Asaresult,themarketpriceofourordinarysharesislikelytobesimilarlyvolatile,andinvestorsinourordinarysharesmayexperienceadecrease,whichcouldbesubstantial,inthevalueoftheirshares,includingdecreasesunrelatedtoouroperatingperformanceorprospects,andcouldlosepartoralloftheirinvestment.Thepriceofourordinarysharescouldbesubjecttowidefluctuationsinresponsetoanumberoffactors,includingthosedescribedelsewhereinthisprospectussupplementortheaccompanyingprospectusandotherssuchas:

• variationsinouroperatingperformanceandtheperformanceofourcompetitors;

• actualoranticipatedfluctuationsinourquarterlyorannualoperatingresults;

• publicationofresearchreportsbysecuritiesanalystsaboutusorourcompetitorsorourindustry;

• ourfailureorthefailureofourcompetitorstomeetanalysts'projectionsorguidancethatweorourcompetitorsmaygivetothemarket;

• additionsanddeparturesofkeypersonnel;

• strategicdecisionsbyusorourcompetitors,suchasacquisitions,divestitures,spin-offs,jointventures,strategicinvestmentsorchangesinbusinessstrategy;

• thepassageoflegislationorotherregulatorydevelopmentsaffectingusorourindustry;

• speculationinthepressorinvestmentcommunity;

• changesinaccountingprinciples;

• terroristacts,actsofwarorperiodsofwidespreadcivilunrest;

• naturaldisastersandothercalamities;and

• changesingeneralmarketandeconomicconditions.

Inthepast,securitiesclassactionlitigationhasoftenbeeninitiatedagainstcompaniesfollowingperiodsofvolatilityintheirshareprice.Thistypeoflitigationcouldresultinsubstantialcostsanddivertourmanagement'sattentionandresources,andcouldalsorequireustomakesubstantialpaymentstosatisfyjudgmentsortosettlelitigation.

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There may be sales of a substantial amount of our ordinary shares after this offering by our current shareholders, and these sales could cause the price of ourordinary shares to fall.

AsofSeptember6,2016,therewere45,145,431ofourordinarysharesoutstanding,excludingtreasuryshares.Ofourissuedandoutstandingshares,alltheordinarysharessoldinourinitialpublicofferingandsubsequentregisteredofferings,includingthisoffering,willbefreelytransferable,exceptforanysharesheldbyour"affiliates,"asthattermisdefinedinRule144undertheSecuritiesAct.FollowingcompletionofthisofferingbasedonthesharesoutstandingasofSeptember6,2016,approximately0.5%ofouroutstandingordinaryshares,excludingtreasuryshares,willbebeneficiallyownedbyourofficersanddirectors.

Certainofourdirectors,executiveofficersandourParenthaveenteredintolock-upagreementswiththeunderwriter,whichregulatetheirsalesofourordinarysharesforaperiodof30daysafterthedateofthisprospectussupplement,subjecttocertainexceptions.

Salesofsubstantialamountsofourordinarysharesinthepublicmarketafterthisoffering,ortheperceptionthatsuchsaleswilloccur,couldadverselyaffectthemarketpriceofourordinarysharesandmakeitdifficultforustoraisefundsthroughsecuritiesofferingsinthefuture.Ofthesharestobeoutstandingaftertheoffering,thesharessoldinourinitialpublicofferingandsubsequentregisteredofferings,includingthesharesofferedbythisprospectussupplementandthesharesissuedunderour2014OmnibusIncentivePlan,areeligibleforimmediatesaleinthepublicmarketwithoutrestrictionbypersonsotherthanouraffiliates.

Inaddition,asofSeptember6,2016,wehad2,523,384ordinarysharesthatwereregisteredandreservedforissuanceunderour2014OmnibusIncentivePlan.

If you purchase shares in this offering, you will suffer immediate and substantial dilution.

AsofJune30,2016,ournettangiblebookvaluepersharewas$4.07.Ifyoupurchaseordinarysharesinthisoffering,youwillincurimmediateandsubstantialdilutionintheproformabookvalueofyourordinarysharesbecausethepricethatyoupaywillbesubstantiallygreaterthanthenettangiblebookvaluedeficiencypershareoftheordinarysharesyouacquire.Youwillexperienceadditionaldilutionupontheexerciseofoptionstopurchaseourordinaryshares,includingthoseoptionscurrentlyoutstandingandthosegrantedinthefuture,andtheissuanceofrestrictedstockunitsorotherequityawardsunderourequityincentiveplans.Totheextentweraiseadditionalcapitalbyissuingequitysecurities,ourshareholderswillexperiencesubstantialadditionaldilution.

The declaration, payment and amount of dividends or other cash distributions to our shareholders will be made at the discretion of our board of directors andwill depend on a number of factors.

OnJune21,2016,ourshareholdersauthorizedourboardofdirectorstomakerepaymentsofequityattimesandinamountssetbytheboard.OnJuly20,2016,wemadearepaymentofequityintheamountof$0.30pershareandanticipatemakingsimilarcashpaymentsinsubsequentquarters.See"DividendPolicy."However,therepaymentofequityorpaymentofdividendswillbeatthediscretionofourboardofdirectorsandourboardofdirectorsmay,initsdiscretion,reduceoreliminatethepaymentofdividendsorothercashdistributionstoourshareholders.Luxembourglawalsolimitstheamountsthatmaybedistributedtoourshareholders.UnderLuxembourglaw,annualcashdividendsmustbepaidfromstatutoryaccountingprofitsandapprovedbyshareholders.Unlessitreceivesdividendsfromitssubsidiaries,TrinseoS.A.willnothavestatutoryaccountingprofitswithoutdividendsfromitssubsidiariesasaholdingcompanywithoutoperations.Theabilitytopaydividendsonourordinarysharesisalsolimitedbyrestrictionsontheabilityofoursubsidiariestopaydividendsormakedistributionstous,includingrestrictionsunderthetermsofthecreditagreementgoverningoursubsidiaries'indebtedness.Additionally,oursubsidiariesarelocatedinavarietyofjurisdictions,which

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couldimposeadditionalrestrictionsorlimitationsontheabilityofthesesubsidiariestopaydividendsormakedistributionstous.

Anyfuturedeterminationtopaydividendsormakeotherdistributionstoourshareholderswillalsodependuponourresultsofoperations,financialcondition,capitalrequirementsandotherfactorsthatourboardofdirectorsdeemsrelevant.

Following the completion of this offering our Parent will no longer own ordinary shares of our Company and as of May 12, 2016 we are no longer a"controlled company" within the meaning of the NYSE rules and the rules of the SEC. We continue to rely on "controlled company" exemptions from certainNYSE and SEC corporate governance requirements during a one-year transition period.

AsofMay12,2016,ourParentnolongercontrolledamajorityofthevotingpowerofouroutstandingordinaryshares.BasedonthenumberofordinarysharesoutstandingasofSeptember6,2016,excludingtreasuryshares,ourParentcurrentlyownsapproximately23.6%ofourordinarysharesand,afterthecompletionofthisoffering,willnotownanyofourordinaryshares.SincetheconsummationofourofferingofordinarysharesinMay2016,wearenolongera"controlledcompany"withinthemeaningofthelistingrulesoftheNYSE.Consequently,undertheNYSElistingrules,wearerequiredtohavecompensationandnominatingandcorporategovernancecommitteescomposedentirelyofindependentdirectorsbyMay12,2017.Duringthistransitionperiod,wemaycontinuetoutilizetheavailableexemptionsfromcertaincorporategovernancerequirementsaspermittedbytheNYSElistingrules.Wecurrentlyrelyontheseexemptionsfromcorporategovernancerequirementsandweintendtorelyonsuchexemptionsforthedurationofthetransitionperiod.Accordingly,duringthetransitionperiod,youwillnothavethesameprotectionsaffordedtoshareholdersofcompaniesthataresubjecttoalloftheNYSEcorporategovernancestandards.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

Thisprospectussupplement,includinginformationincorporatedbyreferenceherein,containsforward-lookingstatementsincluding,withoutlimitation,statementsconcerningplans,objectives,goals,projections,strategies,futureeventsorperformance,andunderlyingassumptionsandotherstatements,whicharenotstatementsofhistoricalfacts.Forward-lookingstatementsmaybeidentifiedbytheuseofwordslike"expect,""anticipate,""intend,""forecast,""outlook,""will,""may,""might,""potential,""likely,""target,""plan,""contemplate,""seek,""attempt,""should,""could,""would"orexpressionsofsimilarmeaning.Forward-lookingstatementsreflectmanagement'sevaluationofinformationcurrentlyavailableandarebasedonourcurrentexpectationsandassumptionsregardingourbusiness,theeconomyandotherfutureconditions.Becauseforward-lookingstatementsrelatetothefuture,theyaresubjecttoinherentuncertainties,risksandchangesincircumstancesthataredifficulttopredict.Specificfactorsthatmayimpactperformanceorotherpredictionsoffutureactionshave,inmanybutnotallcases,beenidentifiedinconnectionwithspecificforward-lookingstatements.Ouractualresultsmaydiffermateriallyfromthosecontemplatedbytheforward-lookingstatements.Theyareneitherstatementsofhistoricalfactnorguaranteesorassurancesoffutureperformance.Importantfactorsthatcouldcauseactualresultstodiffermateriallyfromthoseintheforward-lookingstatementsincludeeconomic,business,competitive,marketandregulatoryconditionsandthefollowing:

• ourcurrentlevelofindebtedness;

• thestabilityofourjointventures;

• changesinregulationsinthejurisdictionswherewemanufacture;

• lawsuitsresultingfromproductsoroperations;

• volatilityincostsordisruptioninthesupplyoftherawmaterialsutilizedforourproducts;

• hazardsassociatedwithchemicalmanufacturing;

• thecompetitivenatureofourendmarkets;

• ourcontinuedrelianceonourrelationshipwithTheDowChemicalCompany;

• ourcompliancewithenvironmental,healthandsafetylaws;

• conditionsintheglobaleconomyandcapitalmarkets;

• anydisruptionsinproductionatourmanufacturingfacilities;

• increasesinthecostofenergy;

• ourabilitytomaintainthenecessarylicensesandpermitsweneedforouroperations;

• failuretomaintainaneffectivesystemofinternalcontrols;

• currentinsurancenotcoveringallpotentialexposures;

• theoutcomeofcertaingovernmentinvestigations;

• changesinlawsandregulationsapplicabletoourbusiness;

• ourdependenceuponkeyexecutivemanagementandanyinabilitytoattractandretainotherqualifiedmanagementpersonnel;

• fluctuationsincurrencyexchangerates;

• strategicacquisitionsaffectingcurrentoperations;

• ourabilitytoreceivedistributionsfromoursubsidiariesandjointventures;

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• theoutcomeoftheongoinginvestigationinvolvingoneofourjointventures;

• thelossofcustomers;

• anyinabilitytocontinuetechnologicalinnovationandsuccessfulintroductionofnewproducts;

• anyinabilitytoprotectourtrademarks,patentsorotherintellectualpropertyrights;

• datasecuritybreaches;

• failureofourassumptionsandprojectionstobeaccurate;

• localbusinessrisksindifferentcountriesinwhichweoperate;

• seasonalityofourbusiness;

• adverseeventsaffectingthestabilityandstandingoftheEuropeanUnion;and

• otherrisksdescribedinthe"RiskFactors"sectionofthisprospectussupplement.

Wederivemanyofourforward-lookingstatementsfromouroperatingbudgetsandforecasts,whicharebaseduponmanydetailedassumptions.Whilewebelievethatourassumptionsarereasonable,wecautionthatitisverydifficulttopredicttheimpactofknownfactors,anditisimpossibleforustoanticipateallfactorsthatcouldaffectouractualresults.Importantfactorsthatcouldcauseactualresultstodiffermateriallyfromourexpectations,orcautionarystatements,aredisclosedunderthesectionentitled"RiskFactors"andthesectionsentitled"Management'sDiscussionandAnalysisofFinancialConditionandResultsofOperations"fromourAnnualReportonForm10-KandfromourQuarterlyReportsonForm10-Q,incorporatedbyreferenceintothisprospectussupplement.Allwrittenandoralforward-lookingstatementsattributabletous,orpersonsactingonourbehalf,areexpresslyqualifiedintheirentiretybythecautionarystatementsaswellasothercautionarystatementsthataremadefromtimetotimeinourotherpubliccommunications.Youshouldevaluateallforward-lookingstatementsmadeinthisprospectussupplementandthedocumentsincorporatedbyreferencehereininthecontextoftheserisksanduncertainties.

Wecautionyouthattheimportantfactorsreferencedabovemaynotcontainallofthefactorsthatareimportanttoyou.Inaddition,wecannotassureyouthatwewillrealizetheresultsordevelopmentsweexpectoranticipateor,evenifsubstantiallyrealized,thattheywillresultintheconsequencesoraffectusorouroperationsinthewayweexpect.Theforward-lookingstatementsincludedinthisprospectussupplementandthedocumentsincorporatedbyreferencehereinaremadeonlyasofthedateoftheapplicabledocument.Weundertakenoobligationtopubliclyupdateorreviseanyforward-lookingstatementasaresultofnewinformation,futureeventsorotherwise,exceptasotherwiserequiredbylaw.

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USE OF PROCEEDS

Wewillnotreceiveanyproceedsfromthesaleofourordinarysharesbythesellingshareholder.

See"SellingShareholder"and"Underwriting."

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MARKET PRICE OF OUR ORDINARY SHARES

OurordinaryshareshavebeenlistedontheNewYorkStockExchangeunderthesymbol"TSE"sinceJune12,2014.Priortothattime,therewasnopublicmarketforourordinaryshares.ThefollowingtablesetsforthfortheperiodsindicatedthehighandlowsalepricesofourordinarysharesontheNewYorkStockExchange.

Arecentreportedclosingpriceforourordinarysharesissetforthonthecoverpageofthisprospectussupplement.AmericanStockTransferandTrustCompany,LLCisthetransferagentandregistrarforourordinaryshares.AsofSeptember6,2016,therewere2holdersofrecordofourordinaryshares.

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Fiscal Quarter High Low 2014: Secondquarter(fromJune12,2014) $ 22.99 $ 20.00Thirdquarter $ 21.78 $ 15.54Fourthquarter $ 18.84 $ 11.922015: Firstquarter $ 20.76 $ 14.14Secondquarter $ 30.44 $ 19.42Thirdquarter $ 33.69 $ 23.46Fourthquarter $ 32.96 $ 24.802016: Firstquarter $ 39.23 $ 21.92Secondquarter $ 49.72 $ 36.19Thirdquarter(throughSeptember19,2016) $ 60.02 $ 41.60

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DIVIDEND POLICY

Wemadearepaymentofequityof$0.30perordinarysharepayableincashonJuly20,2016toourshareholdersofrecordasofthecloseofbusinessonJuly6,2016.Priortothisdistribution,wehadnotdeclaredorpaiddividendsorothercashdistributionsonourordinarysharessincebecomingapubliccompany.

Luxembourglawpermitscashdistributionstoshareholdersthroughtherepaymentofshareholders'equity.Theamountofthisdistributionmaynotcausetheannualnon-consolidatedstatutorynetassetsofTrinseoS.A.tofallbelowtheaggregateofitsissuedandsubscribedsharecapitalandlegalreserves.Weexpectthatourreservesavailablefordistributionwillpermitustomakecashdistributionstoourshareholdersinto2017.OurshareholdershaveauthorizedourboardofdirectorstomakeequityrepaymentsinamountsandinfrequenciesdeterminedbytheboardofdirectorsandatalltimesincompliancewithLuxembourglaw.Nevertheless,thisauthorizationfromourshareholdersdoesnotrequirethatourboardofdirectorsdeclareandmakeanequityrepayment,orguaranteethattheywillcontinuedosointhefuture.

PaymentofdividendsonourordinarysharesissubjecttothedeterminationanddeclarationbyourboardofdirectorsandtheapprovalofourshareholdersunderLuxembourglaw.Luxembourglawalsolimitstheamountsthatmaybedistributedtoourshareholders.UnderLuxembourglaw,cashdividendsmustbepaidfromstatutoryaccountingprofitsandapprovedbyshareholders.Unlessitreceivesdividendsfromitssubsidiaries,TrinseoS.A.willnothavestatutoryaccountingprofitsasaholdingcompanywithoutoperations.

Theabilitytopaydividendsonourordinarysharesisalsolimitedbyrestrictionsontheabilityofoursubsidiariestopaydividendsormakedistributionstous,includingrestrictionsunderthetermsofthecreditagreementgoverningoursubsidiaries'indebtedness.Additionally,oursubsidiariesarelocatedinavarietyofjurisdictions,whichcouldimposeadditionalrestrictionsorlimitationsontheabilityofthesesubsidiariestopaydividendsormakedistributionstous.

Althoughweexpecttocontinuetomakequarterlycashdistributionstoshareholdersasrepaymentsofequityordividends,anyfuturedeterminationtopaydividendsormakeotherdistributionstoourshareholderswillbeatthediscretionofourboardofdirectors,subjecttocompliancewithcovenantsincurrentandfutureagreementsgoverningourindebtednessandapplicableLuxembourglaw,andwilldependuponourresultsofoperations,financialcondition,capitalrequirementsandotherfactorsthatourboardofdirectorsdeemsrelevant.

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DESCRIPTION OF SHARE CAPITAL

Thefollowingisasummaryofsomeofthetermsofourordinaryshares,basedonourarticlesofassociation.

Thefollowingsummaryissubjectto,andisqualifiedinitsentiretybyreferenceto,theprovisionsofourarticlesofassociation,theformofwhichhasbeenfiledasanexhibittotheregistrationstatementofwhichthisprospectusisapart.Youmayobtaincopiesofourarticlesofassociationasdescribedunder"WhereYouCanFindMoreInformation"inthisprospectus.

General

TrinseoS.A.isaLuxembourgpubliclimitedliabilitycompany(société anonyme ).Thecompany'slegalnameis"TrinseoS.A."TrinseoS.A.wasincorporatedonJune3,2010asaLuxembourgprivatelimitedliabilitycompany(société à responsabilité limitée )andwasconvertedintoaLuxembourgpubliclimitedliabilitycompanyonApril29,2011.

TrinseoS.A.isregisteredwiththeLuxembourgRegistryofTradeandCompaniesundernumberB153.549.TrinseoS.A.hasitsregisteredofficeat4,rueLouHemmer,L-1748Luxembourg,GrandDuchyofLuxembourg.

ThecorporatepurposeofTrinseoS.A.isstatedinArticle3ofitsarticlesofassociation.Thispurposeincludestheacquisitionofparticipations,inLuxembourgorabroad,inanycompanyorenterpriseinanyformwhatsoever,andthemanagement,developmentandsaleofthoseparticipations.TrinseoS.A.mayacquireandsell,bysubscription,purchaseandexchangeorinanyothermanner,anystock,sharesandotherparticipationsecurities,bonds,debentures,certificatesofdepositandotherdebtinstrumentsand,moregenerally,anysecuritiesandfinancialinstrumentsissuedbyanypublicorprivateentity.Itmayparticipateinthecreation,development,managementandcontrolofanycompanyorenterprise.Furthermore,itmayinvestintheacquisitionandmanagementofaportfolioofpatentsorotherintellectualpropertyrightsofanynatureororigin.

Additionally,TrinseoS.A.mayborrowinanyformandproceedtoissuedebtbyprivateorpublicofferingsofbonds,convertiblebondsanddebenturesoranyothersecuritiesorinstrumentsitdeemsfit.Ingeneral,TrinseoS.A.maygrantassistance(bywayofloans,advances,guaranteesorsecuritiesorotherwise)tocompaniesorotherenterprisesinwhichTrinseoS.A.hasaninterestorwhichformpartofthegroupofcompaniestowhichTrinseoS.A.belongsoranyotherentityasTrinseoS.A.maydeemfit.

TrinseoS.A.mayuseanytechniques,legalmeansandinstrumentstomanageitsinvestmentsintheparticipationsefficientlyandprotectitselfagainstcreditrisks,currencyexchangeexposure,interestraterisks,andotherrisk.Finally,itcanalsoperformallcommercial,financialorindustrialoperationandanytransactionwithrespecttorealestateormovableproperty,whichdirectlyorindirectlysupportsorrelatestoitscorporatepurpose.

Share Capital

AsofSeptember6,2016,ourissuedsharecapitalamountsto$487,779.34,representedby48,777,934issuedordinaryshares,including3,632,503ordinarysharesheldintreasury,eachwithanominalvalueof$0.01pershare.Allissuedshareswerefullypaid.OurtreasuryshareshavenovotingrightsoranyrightstoreceivedividendsorotherdistributionsmadebytheCompany.

Ourarticlesofassociationauthorizeourboardofdirectorstoissueordinaryshareswithinthelimitsoftheauthorizedsharecapitalatsuchtimesandonsuchtermsasourboardofdirectorsmaydecideforaperiodcommencingonthedateofpublicationofouramendedarticlesofassociation(i.e.,June11,2014)andendingfiveyearsafterthedateonwhichtheminutesoftheshareholders'

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meetingapprovingsuchauthorizationarepublishedintheLuxembourgofficialgazette(RecueildesSociétésetAssociations(RESA ))(unlesssuchperiodisextended,amendedorrenewed).Accordingly,ourboardisauthorizedtoissueupto50,000,000,000ordinarysharesduringsuchperiod.Wecurrentlyintendtoseekrenewalsand/orextensionsasrequiredfromtimetotime.

Ourauthorizedsharecapitalisdeterminedbyourarticlesofassociation,asamendedfromtimetotime,andmaybeincreased,reducedorextendedbyamendingthearticlesofassociationbyapprovaloftherequisitetwo-thirdsmajorityofthevotesataquorateextraordinarygeneralshareholders'meeting.

UnderLuxembourglaw,ourshareholdersbenefitfromapre-emptivesubscriptionrightontheissuanceofsharesforcashconsideration.However,ourshareholdershave,inaccordancewithLuxembourglaw,authorizedtheboardofdirectorstosuppress,waiveorlimitanypre-emptivesubscriptionrightsofshareholdersprovidedbylawtotheextenttheboarddeemssuchsuppression,waiverorlimitationadvisableforanyissuanceorissuancesofshareswithinthescopeofourauthorizedsharecapital.Suchsharesmaybeissuedabove,atorbelowmarketvaluebutinanyeventnotbelowthenominalvalueperordinaryshareaswellasbywayofincorporationofavailablereserves(includingpremium).

Theboardofdirectorswillresolveonasharesissuanceforwhichitintendstowaiveorlimitanypre-emptivesubscriptionrightsofshareholdersinaccordancewiththequorumandvotingthresholdssetforthinourarticlesofassociation.Theboardofdirectorswillalsoresolveontheapplicableproceduresandtimelinestowhichitwill,orhasto,subjectsuchissuance.Iftheproposaloftheboardofdirectorstoissuenewsharesexceedsthelimitsoftheourauthorizedsharecapital,theboardofdirectorsmustthenconvenetheshareholderstoanextraordinarygeneralmeetingtobeheldinthepresenceofaLuxembourgnotaryforthepurposeofincreasingtheissuedsharecapitalaccordinglyandprioritizingtheissueofsharesexceedingthelimitoftheauthorizedsharecapital.Thismeetingwillbesubjecttothetwo-thirdmajorityofthevotesataquorateextraordinarygeneralshareholders'meeting.Ifacapitalcallproposedbytheboardofdirectorsconsistsofanincreaseintheshareholders'commitments,theboardofdirectorsmustthenconvenetheshareholderstoanextraordinarygeneralmeetingtobeheldinthepresenceofaLuxembourgnotaryforsuchpurpose.Thismeetingwillbesubjecttotheunanimousconsentoftheshareholders.

Form and Transfer of Shares

OurordinarysharesareissuedinregisteredformonlyandarefreelytransferableunderLuxembourglawandourarticles,providedthatourboardofdirectorsmayimposetransferrestrictionsforsharesthatareregistered,listed,quoted,dealtin,orhavebeenplacedincertainjurisdictionsincompliancewiththeapplicablerequirements.LuxembourglawdoesnotimposeanylimitationsontherightsofLuxembourgornon-Luxembourgresidentstoholdorvoteourordinaryshares.UnderLuxembourglaw,theownershipofregisteredsharesisestablishedbytheinscriptionofthenameoftheshareholderandthenumberofsharesheldbyhimorherintheshareholdersregister(registre des actionnaires )heldbyusatourregisteredofficeinLuxembourg.Atalltimes,wekeepacopyoftheshareholdersregisterinatourregisteredofficeinLuxembourg.Eachtransferofsharesshallbepromptlymadeknowntousaswellasanychangestotheshareholdersregisterandwerecordsuchchangeintheshareholdersregisterheldatourregisteredoffice.ForpurposesofLuxembourglaw,ownershipofourordinarysharesisevidencedthroughregistrationfromtimetotimeintheshareholdersregisterheldatourregisteredoffice,andsuchregistrationisameansofevidencingtitletotheshares.Fortheavoidanceofdoubt,incaseofdiscrepancybetweentheshareholdersregisterheldbyusatourregisteredofficeinLuxembourgandanyotherseparateregisterforthesharesheldbyentitiesinLuxembourgorinotherjurisdictions,theshareholdersregister(registre des actionnaires )heldbyusatourregisteredofficeinLuxembourgshallprevail.

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Withoutprejudicetotheconditionsfortransferbybookentrywheresharesarerecordedintheshareholderregisteronbehalfofoneormorepersonsinthenameofadepository,eachtransferofsharesshallbeeffectedbywrittendeclarationoftransfertoberecordedintheshareholderregister,suchdeclarationtobedatedandsignedbythetransferorandthetransferee,orbytheirdulyappointedagents.Wemayacceptandenterintotheshareholderregisteranytransferofshareseffectedpursuanttoanagreementoragreementsbetweenthetransferorandthetransferee,trueandcompletecopiesofwhichhavebeendeliveredtous.

Ourarticlesofassociationprovidethatwemayappointregistrarsindifferentjurisdictions,eachofwhommaymaintainaseparateregisterforthesharesenteredinsuchregisterandtheholdersofsharesshallbeenteredintooneoftheregistersandpromptlymadeknowntousforpurposesofregistrationintheshareholders'register(registre des actionnaires )heldbyusatourregisteredofficeinLuxembourg.Shareholdersmayelecttobeenteredintooneoftheseregistersandtotransfertheirsharestoanotherregistersomaintained.Entriesintheseregistersisreflectedintheshareholders'registermaintainedatourregisteredoffice.

Inaddition,ourarticlesofassociationalsoprovidethatourordinarysharesmaybeheldthroughasecuritiessettlementsystemoraprofessionaldepositoryofsecurities.Ordinarysharesheldinsuchmannerhavethesamerightsandobligationsasordinarysharesrecordedinourshareholders'register.Furthermore,ordinarysharesheldthroughasecuritiessettlementsystemoraprofessionaldepositoryofsecuritiesmaybetransferredinaccordancewithcustomaryproceduresforthetransferofsecuritiesinbook-entryform,thetransferbeingeffectiveuponnotificationtousandregistrationintheshareholders'register(registre desactionnaires )heldbyusatourregisteredofficeinLuxembourg.

Issuance of Shares

PursuanttotheLuxembourglawoncommercialcompaniesdatedAugust10,1915,asamended,whichwerefertoastheLuxembourgCorporateLaw,theissuanceofordinarysharesrequirestheamendmentofourarticlesofassociationbyapprovaloftherequisitetwo-thirdsmajorityofthevotesataquorateextraordinarygeneralshareholders'meeting(see"—GeneralMeetingofShareholders"and"—AmendmenttotheArticlesofAssociation").ThegeneralmeetingmaydetermineanauthorizedsharecapitalandauthorizetheboardofdirectorstoissueordinarysharesuptothemaximumamountofsuchauthorizedsharecapitalforamaximumperiodoffiveyearsasfromthedateofpublicationintheLuxembourgofficialgazette(Recueil Electronique des Sociétés et Associations (RESA))oftheminutesoftherelevantgeneralmeeting.Thegeneralmeetingofshareholdersmayamend,reneworextendsuchauthorizedsharecapitalandsuchauthorizationtotheboardofdirectorstoissueshares.

Ourarticlesprovidethatnofractionalsharesshallbeissued.

Ourordinaryshareshavenoconversionrightsandtherearenoredemptionorsinkingfundprovisionsapplicabletoourordinaryshares.

Pre-Emptive Rights

Unlesslimited,waivedorcancelledbyourboardofdirectors,holdersofourordinaryshareshaveaproratapre-emptiverighttosubscribeforanynewsharesissuedforcashconsideration.Ourarticlesofassociationprovidethatpre-emptiverightscanbelimited,waivedorcancelledbyourboardofdirectorsforaperiodendingonthefifthanniversaryofthedateonwhichtheminutesoftheshareholders'meetingapprovingsuchauthorizationarepublishedintheLuxembourgOfficialGazette(RESA ),meaningJune11,2019,unlesssuchperiodisextended,amendedorrenewed,intheeventofanincreaseofthesharecapitalbytheboardofdirectorswithinthelimitsoftheauthorizedsharecapital.

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Repurchase of Shares

Wecannotsubscribeforourownordinaryshares.

Wemay,however,repurchaseissuedordinarysharesorhaveanotherpersonrepurchaseissuedordinarysharesforouraccount,subjecttothefollowingconditions:

• priorauthorizationbyasimplemajorityvoteatanordinarygeneralmeetingofshareholders,whichauthorizationsetsforththetermsandconditionsoftheproposedrepurchaseandinparticularthemaximumnumberofordinarysharestoberepurchased,thedurationoftheperiodforwhichtheauthorizationisgiven(whichmaynotexceedfiveyears)and,inthecaseofrepurchaseforconsideration,theminimumandmaximumconsiderationpershare;

• therepurchasemaynotreduceournetassetsonanon-consolidatedbasistoalevelbelowtheaggregateoftheissuedandsubscribedsharecapitalandthereservesthatwemustmaintainpursuanttoLuxembourglaworourarticlesofassociation;

• onlyfullypaid-upsharesmayberepurchased;and

• theoffertoacquiremustbemadeonthesameconditionstoallsimilarlysituatedshareholders,exceptforacquisitions:(i)decidedunanimouslyatageneralmeetingatwhichalltheshareholderswerepresentorrepresented;or(ii)bylistedcompaniesonthestockexchange.

Thegeneralmeetingofshareholdersauthorizedtheboardofdirectorstorepurchaseupto4.5millionofitsordinaryshares.Theauthorizationisvalidforaperiodendingontheearlierof2yearsfromthedateofthedecision(meaninguntilJune21,2018)orthedateofitsrenewalbyasubsequentgeneralmeetingofshareholders.Pursuanttosuchauthorization,theboardofdirectorsisauthorizedtoacquireandsellordinarysharesintheCompanyundertheconditionssetforthinArticle49-2oftheLuxembourgCorporateLaw.Suchpurchasesandsalesmaybecarriedoutforanyauthorizedpurposeoranypurposethatisauthorizedbythelawsandregulationsinforce.

Thepurchasepriceperordinarysharetobepaidshallnotrepresentmorethan$1,000andshallnotbelessthan$1.00.

Inaddition,pursuanttoLuxembourglaw,TrinseoS.A.maydirectlyorindirectlyrepurchaseordinarysharesbydecisionofourboardofdirectorswithoutthepriorapprovalofthegeneralmeetingofshareholdersifsuchrepurchaseisdeemedbytheboardofdirectorstobenecessarytopreventseriousandimminentharmtousoriftheacquisitionofshareshasbeenmadeinviewofthedistributionthereoftoemployees.

Capital Reduction

Ourarticlesofassociationprovidethatourissuedsharecapitalmaybereduced,subjecttotheapprovalorpriorauthorizationoftherequisitetwo-thirdsmajorityofthevotesataquorateextraordinarygeneralshareholders'meeting.

General Meeting of Shareholders

AnyregularlyconstitutedgeneralmeetingofshareholdersofTrinseoS.A.representstheentirebodyofshareholdersofTrinseoS.A.

Eachofourordinarysharesentitlestheholderthereoftoattendourgeneralmeetingofshareholders,eitherinpersonorbyproxy,toaddressthegeneralmeetingofshareholders,andtoexercisevotingrights,subjecttotheprovisionofourarticlesofassociation.Eachordinaryshareentitlestheholdertoonevoteatageneralmeetingofshareholders.Ourarticlesofassociationprovidethatourboardofdirectorsshalladoptallotherregulationsandrulesconcerningtheattendancetothe

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generalmeeting,andavailabilityofaccesscards,proxyformsinordertoenableshareholderstoexercisetheirrighttovoteasitdeemsfit.

Ashareholdermayparticipateatanygeneralmeetingofshareholdersbyappointinganotherperson(whoneednotbeashareholder)ashisproxy,theappointmentofwhichshallbeinwriting.Ourarticlesofassociationprovidethatourboardofdirectorsmaydetermineadatebywhichweorouragentsmusthavereceiveddulycompletedproxyformsinorderforsuchformtobetakenintoaccountatthegeneralmeeting.

Whenconveningageneralmeetingofshareholders,wewillpublishanotice(whichmustbepublishedatleast30dayspriortothegeneralmeetingdate)intheRESA ,andinaLuxembourgnewspaper.OurarticlesofassociationprovidethatnoticeoftheconveningofthegeneralmeetingofshareholderswillalsobeprovidedinaformofeasilyaccessiblemediawhichisreasonablyexpectedtoberelieduponfortheeffectivedisseminationofinformationtothepublicandthroughouttheEuropeanEconomicArea.

Therightofashareholdertoparticipateinageneralmeetingofshareholdersandexercisevotingrightsisdeterminedbyreferencetothenumberofsharesheldbytheshareholderatmidnight(00:00)ontherecorddate,whichmaybethedayfalling14daysbeforethedateofthegeneralmeetingofshareholdersoranotherdaysetbyourboardofdirectorsandmentionedintheconveningnotice.Eachshareholdershall,onorbeforetherecorddate,indicatetousitsintentiontoparticipateinpersonatthegeneralmeetingofshareholders.TrinseoS.A.determinesthemannerinwhichthisdeclarationismade.Proofofthequalificationasashareholdermayonlybethosenecessarytoensuretheidentificationofshareholders.OurBoardmaydetermineanyotherconditionsthatmustbefulfilledbytheshareholdersforthemtotakepartinanygeneralmeetingofshareholdersinpersonorinproxy.

TheannualordinarygeneralmeetingofshareholdersofTrinseoS.A.isheldat2:00p.m.(CentralEuropeanTime)onthefirstMondayofJuneofeachyearattheregisteredofficeoftheCompanyorinanyotherplacewithinthemunicipalityoftheregisteredofficeoftheCompanyintheGrandDuchyofLuxembourg,asnoticedtotheshareholders,orabroad,iftheboardofdirectorsconsidersinitsabsoluteandfinaljudgment,thatexceptionalcircumstancessorequire.IfthatdayisnotabusinessdayinLuxembourg,themeetingwillbeheldonthenextfollowingbusinessday.

Luxembourglawprovidesthattheboardofdirectorsisobligedtoconveneageneralmeetingofshareholdersifshareholdersrepresenting,intheaggregate,10%oftheissuedsharecapitalsorequestinwritingwithanindicationofthemeetingagenda.Insuchcase,thegeneralmeetingofshareholdersmustbeheldwithinonemonthoftherequest.Iftherequestedgeneralmeetingofshareholdersisnotheldwithinonemonth,shareholdersrepresenting,intheaggregate,10%oftheissuedsharecapitalmaypetitionthecompetentpresidentofthedistrictcourtinLuxembourgtohaveacourtappointeeconvenethemeeting.Luxembourglawprovidesthatshareholdersrepresenting,intheaggregate,10%oftheissuedsharecapitalmayrequestthatadditionalitemsbeaddedtotheagendaofageneralmeetingofshareholders.ThatrequestmustbemadebyregisteredmailsenttotheregisteredofficeoftheCompanyatleastfivedaysbeforethegeneralmeetingofshareholders.

Voting Rights

Eachshareentitlestheholderthereoftoonevoteatageneralmeetingofshareholders.Luxembourglawdistinguishesordinaryresolutionsandextraordinaryresolutions.

Extraordinaryresolutionsrelatetoproposedamendmentstothearticlesofassociationandcertainotherlimitedmatters.Allotherresolutionsareordinaryresolutions.

Ordinary Resolutions

Pursuanttoourarticlesofassociation,foranyordinaryresolutionstobeconsideredatageneralmeeting,thequorumatsuchmeetingmustbeatleastfiftypercent(50%)oftheissuedsharecapitaloftheCompany(unlessotherwisemandatorilyrequiredbylaw)andsuchordinaryresolutionsshallbeadoptedbyasimplemajorityofvotesvalidlycastonsuchresolution.Abstentionsarenotconsidered"votes."

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Extraordinary Resolutions

Extraordinaryresolutionsarerequiredforanyofthefollowingmatters,amongothers:(a)anincreaseordecreaseoftheauthorizedorissuedcapital,(b)alimitationorexclusionofpreemptiverights,(c)approvalofastatutorymergerorde-merger(scission),(d)dissolutionandliquidationofTrinseoS.A.and(e)anyandallamendmentstoourarticlesofassociation.Pursuanttoourarticlesofassociation,foranyextraordinaryresolutionstobeconsideredatageneralmeetingthequorumshallbeatleastone-half(50%)oftheissuedsharecapitaloftheCompanyunlessotherwisemandatorilyrequiredbylaw.Ifthesaidquorumisnotpresent,asecondmeetingmaybeconvenedatwhichnoquorumconditionshallapply.Anyextraordinaryresolutionshallbeadoptedataquorategeneralmeeting(saveasotherwiseprovidedbymandatorylaw)atleasttwo-thirds(2/3)majorityofthevotesvalidlycastonsuchresolution.Abstentionsarenotconsideredvotes.

Appointment and Removal of Directors

Membersofourboardofdirectorsmaybeelectedbyordinaryresolutionatageneralmeetingofshareholdersatasimplemajorityvoteofshareholders.Ourarticlesofassociationprovidethatalldirectorsareelectedforaperiodofthreeyears,withtheboarddividedintothreeclassesofapproximatelyequalsize.Attheannualgeneralmeetingofshareholders,oneclassperyearwillbeelected.Anydirectormayberemovedwithorwithoutcausebyordinaryresolutionatageneralmeetingofshareholders.Ourarticlesofassociationprovidethatincaseofavacancy,theotherdirectorsshallfillsuchvacancyonaprovisionalbasis,until(i)thedecisionisratifiedor(ii)anewdirectoriselected,byanordinaryresolutionofthenextgeneralmeetingofshareholders.Thedirectorsshallbeeligibleforre-electionindefinitely.

NeitherLuxembourglawnorourarticlesofassociationcontainanyrestrictionsastothevotingofoursharesbynon-Luxembourgresidents.

Amendment to the Articles of Association

Shareholder Approval Requirements

Luxembourglawrequiresthatanamendmentofthearticlesofassociationbemadebyextraordinaryresolution,suchdecisionbeingtakenwithaqualifiedmajorityofvotes.Theagendaofthegeneralmeetingofshareholdersmustindicatetheproposedamendmentstothearticlesofassociation.

Formalities

AnyresolutionstoamendourarticlesofassociationmustbetakenbeforeaLuxembourgnotaryandsuchamendmentsmustbepublishedinaccordancewithLuxembourglaw.

Merger and De-Merger

Amergerorde-mergerbyabsorptionwherebyoneLuxembourgcompanyafteritsdissolutionwithoutliquidationtransferstoanothercompanyallofitsassetsandliabilitiesinexchangefortheissuanceofsharesintheacquiringcompanytotheshareholdersofthecompanybeingacquired,oramergerorde-mergereffectedbytransferofassetstoanewlyincorporatedcompany,must,inprinciple,beapprovedatageneralmeetingbyanextraordinaryresolutionoftheLuxembourgcompany,andthegeneralmeetingmustbeheldbeforeanotary.

Dissolution and Liquidation

Intheeventofourdissolution,liquidation,orwinding-uptheassetsremainingafterallowingforthepaymentofallliabilitiesofthecompanywillbepaidouttotheshareholdersprorataaccordingtotheirrespectiveshareholdings.Generallythedecisionstodissolve,liquidate,orwind-uprequirethepassingofanextraordinaryresolutionatageneralmeetingofourshareholders,andsuchmeetingmust

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beheldbeforeanotary.ShareholdersofaLuxembourgpubliclimitedliabilitycompanyhavetheirliabilitylimitedtothecapitalcontributioninrespectofthesharestheysubscribedandpaidorcommittedtopayfor.However,distributionofdividendsbytheCompanymaynotresultinareductionoftheCompany'snetassetvaluebelowtheamountofitscapital.

No Appraisal Rights

NeitherLuxembourglawnorourarticlesofassociationprovideforanyappraisalrightsofdissentingshareholders.

Dividend Distributions

SubjecttoLuxembourglaw,ifandwhenadividenddistributionisdeclaredbythegeneralmeetingofshareholdersortheboardofdirectorsinthecaseofinterimdividenddistributions,eachordinaryshareisentitledtoparticipateequallyinsuchdistributionoffundslegallyavailableforsuchpurposes.Pursuanttoourarticlesofassociation,thegeneralmeetingofshareholdersmayapproveadividenddistributionandtheboardofdirectorsmaydeclareaninterimdividenddistribution,totheextentpermittedbyLuxembourglaw.

Declaredandunpaiddividenddistributionsheldbyusfortheaccountoftheshareholdersshallnotbearinterest.UnderLuxembourglaw,claimsforunpaiddividenddistributionswilllapseinourfavorfiveyearsafterthedatesuchdividenddistributionwasdeclared.

Annual Accounts

UnderLuxembourglaw,theboardofdirectorsmustprepareunconsolidatedannualaccounts,i.e.,aninventoryoftheassetsandliabilitiesofTrinseoS.A.togetherwithabalancesheetandaprofitandlossaccounteachyear.Ourboardofdirectorsmustalsoannuallyprepareconsolidatedaccountsandmanagementreportsontheunconsolidatedannualaccountsandconsolidatedaccounts.Theunconsolidatedannualaccounts,theconsolidatedaccounts,themanagementreportandtheauditor'sreportsmustbeavailableforinspectionbyshareholdersuponrequestandfreeofcharge,atourregisteredofficeatleast15calendardayspriortothedateoftheannualordinarygeneralmeetingofshareholders.

Theunconsolidatedannualaccountsandtheconsolidatedaccounts,afterapprovalbytheannualordinarygeneralmeetingofshareholders,willbefiledwiththeLuxembourgRegistryofTradeandCompanies.

Information Rights

Luxembourglawgivesshareholderslimitedrightstoinspectcertaincorporaterecords8calendardayspriortothedateoftheannualordinarygeneralmeetingofshareholders,includingtheunconsolidatedannualaccountswiththelistofdirectorsandauditors,theconsolidatedaccounts,thenotestotheannualaccountsandtheconsolidatedaccounts,alistofshareholderswhosesharesarenotfullypaid-up,themanagementreportsandtheauditor'sreport.

Inaddition,anyregisteredshareholderisentitledtoreceiveacopyoftheunconsolidatedannualaccounts,theconsolidatedaccounts,theauditor'sreportsandthemanagementreportsfreeofchargepriortothedateoftheannualordinarygeneralmeetingofshareholders.

UnderLuxembourglaw,itisgenerallyacceptedthatashareholderhastherighttoreceiveresponsesattheshareholders'generalmeetingtoquestionsconcerningitemsontheagendaofthatgeneralmeetingofshareholders,ifsuchresponsesarenecessaryorusefulforashareholdertomakeaninformeddecisionconcerningsuchagendaitem,unlessaresponsetosuchquestionscouldbedetrimentaltoourinterests.

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Board of Directors

ThemanagementofTrinseoS.A.isvestedinaboardofdirectors(conseil d'administration ).Ourarticlesofassociationprovidethattheboardofdirectorsmustcompriseatleastthreemembersandnomorethantwelvemembers.

TheboardofdirectorsmeetsasoftenasCompanyinterestsrequire.

Amajorityofthemembersoftheboardpresentorrepresentedataboardmeetingconstitutesaquorum,andresolutionsareadoptedbythesimplemajorityvoteoftheboardmemberspresentorrepresented.Theboardmayalsotakedecisionsbymeansofresolutionsinwritingsignedbyalldirectors.Eachdirectorhasonevote.Thegeneralshareholders'meetingelectsdirectorsanddecidestheirrespectiveterms.Pursuanttoourarticlesofassociation,thetermofofficeofthedirectorsis3yearsbuttheymaybere-elected.Thegeneralshareholders'meetingmaydismissoneormoredirectorsatanytime,withorwithoutcausebyanordinaryresolution.Iftheboardhasavacancy,theremainingdirectorsmustfillsuchvacancyonatemporarybasispursuanttotheaffirmativevoteofamajorityoftheremainingdirectors.Thetermofatemporarydirectorelectedtofillavacancyexpiresattheendofthetermofofficeofthereplaceddirector,provided,however,thatthenextgeneralshareholders'meetingshallberequesteddefinitivelytoelectanytemporarydirector.

Withinthelimitsprovidedforbylaw,ourboardmaydelegatetooneormorepersonsthedailymanagementoftheCompanyandtheauthoritytorepresenttheCompany.

Nodirectorshall,solelyasaresultofbeingadirector,bepreventedfromcontractingwithus,eitherwithregardtohistenureinanyofficeorplaceofprofitorasvendor,purchaserorinanyothermannerwhatsoever,norshallanycontractinwhichanydirectorisinanywayinterestedbeliabletobevoidedmerelyonaccountofhispositionasdirector,norshallanydirectorwhoissointerestedbeliabletoaccounttousortheshareholdersforanyremuneration,profitorotherbenefitrealizedbythecontractbyreasonofthedirectorholdingthatofficeorofthefiduciaryrelationshiptherebyestablished.

Anydirectorhavinganinterestinatransactionsubmittedforapprovaltotheboardmayparticipateinthedeliberationsandvotethereon,unlessthetransactionisnotintheordinarycourseoftheCompany'sbusinessandthatconflictswiththeCompany'sinterest,inwhichcasethedirectorshallbeobligedtoadvisetheboardthereofpriortothevoteandtocausearecordofhisstatementtobeincludedintheminutesofthemeeting.Hemaynottakepartinthesedeliberationsnorvoteonsuchatransaction.Atthenextgeneralmeeting,beforeanyotherresolutionisputtoavote,aspecialreportshallbemadeonanytransactionsinwhichanyofthedirectorsmayhavehadaninterestthatconflictswithourinterest.

NoshareholdingqualificationfordirectorsisrequiredunderLuxembourglaw.

Ourarticlesofassociationprovidethatdirectorsandofficers,pastandpresent,areentitledtoindemnificationfromustothefullestextentpermittedbyLuxemburglawagainstliabilityandallexpensesreasonablyincurredorpaidbyhiminconnectionwithanyclaim,action,suitorproceedinginwhichheisinvolvedbyvirtueofhisbeingorhavingbeenadirectororofficerandagainstamountspaidorincurredbyhiminthesettlementthereof.Wemaypurchaseandmaintaininsuranceforanydirectororotherofficeragainstanysuchliability.

Noindemnificationwillbeprovidedagainstanyliabilitytousorourshareholdersbyreasonofwillfulmisfeasance,badfaith,grossnegligenceorrecklessdisregardofthedutiesofadirectororofficeroranymatterastowhichanydirectororofficershallhavebeenfinallyadjudicatedtohaveactedinbadfaithandnotintheinterestoftheCompany.

Transfer Agent and Registrar

ThetransferagentandregistrarforourordinarysharesisAmericanStockTransferandTrustCompany,LLC.

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MATERIAL UNITED STATES FEDERAL INCOME AND LUXEMBOURG TAX CONSIDERATIONS

United States Federal Income Tax Considerations

Subjecttothelimitationsandqualificationsstatedherein,thisdiscussionsetsforththematerialU.S.federalincometaxconsequencesoftheownershipanddispositionbyU.S.Holders(asdefinedbelow)oftheordinaryshares.ThediscussionisbasedontheU.S.InternalRevenueCodeof1986,asamended,itslegislativehistory,existingandproposedregulationsthereunder,publishedrulingsandcourtdecisions,allascurrentlyineffectandallsubjecttochangeatanytime,possiblywithretroactiveeffect.ThissummaryappliesonlytoU.S.Holdersanddoesnotaddresstaxconsequencestoanon-U.S.Holderinvestinginourordinaryshares.

ThediscussionofaU.S.Holder'staxconsequencesaddressesonlythoseU.S.Holdersthatacquiretheirordinarysharesinthisofferingandthatholdthoseordinarysharesascapitalassetsanddoesnotaddressthetaxconsequencestoanyspecialclassofholders,includingwithoutlimitation,holders(directly,indirectlyorconstructively)of10%ormoreofourshares,dealersinsecuritiesorcurrencies,banks,tax-exemptorganizations,lifeinsurancecompanies,financialinstitutions,broker-dealers,regulatedinvestmentcompanies,realestateinvestmenttrusts,tradersinsecuritiesthatelectthemark-to-marketmethodofaccountingfortheirsecuritiesholdings,personsthatholdsecuritiesthatareahedgeorthatarehedgedagainstcurrencyorinterestraterisksorthatarepartofastraddle,conversionor"integrated"transaction,U.S.expatriates,partnershipsorotherentitiesclassifiedaspartnershipsforU.S.federalincometaxpurposesandU.S.HolderswhosefunctionalcurrencyforU.S.federalincometaxpurposesisnottheU.S.dollar.ThisdiscussiondoesnotaddresstheeffectoftheU.S.federalalternativeminimumtax,orU.S.federalestateandgifttax,oranystate,localorforeigntaxlawsonaholderofordinaryshares.

Forpurposesofthisdiscussion,a"U.S.Holder"isabeneficialownerofordinarysharesthatisforU.S.federalincometaxpurposes:(a)anindividualwhoisacitizenorresidentoftheUnitedStates;(b)acorporation(orotherentitytaxableasacorporationforU.S.federalincometaxpurposes)createdororganizedinorunderthelawsoftheUnitedStates,anystatethereofortheDistrictofColumbia;(c)anestatetheincomeofwhichissubjecttoU.S.federalincometaxationregardlessofitssource;or(d)atrust(i)ifacourtwithintheUnitedStatescanexerciseprimarysupervisionoveritsadministration,andoneormoreU.S.personshavetheauthoritytocontrolallofthesubstantialdecisionsofthattrust,or(ii)thatwasinexistenceonAugust20,1996andvalidlyelectedunderapplicableTreasuryRegulationstocontinuetobetreatedasadomestictrust.Theterm"non-U.S.Holder"meansanybeneficialownerofourordinarysharesthatisnotaU.S.Holder,apartnership(oranentityorarrangementthatistreatedasapartnershipforU.S.federalincometaxpurposes)orapersonholdingourordinarysharesthroughapartnership.

IfapartnershiporanentityorarrangementthatistreatedasapartnershipforU.S.federalincometaxpurposesholdsourordinaryshares,thetaxtreatmentofapartnerwillgenerallydependuponthestatusofthepartnerandtheactivitiesofthepartnership.Partnersinpartnershipsthatholdourordinarysharesshouldconsulttheirowntaxadvisors.

You are Urged to Consult Your Own Independent Tax Advisor Regarding the Specific U.S. Federal, State, Local and Foreign Income and OtherTax Considerations Relating to the Ownership and Disposition of Our Ordinary Shares.

Cash Dividends and Other Distributions

Asdescribedinthesectionentitled"DividendPolicy,"weexpecttomakequarterlycashdistributionstoourshareholdersasrepaymentsofequityordividends,however,anyfuturedeterminationtopaydividendsormakeotherdistributionstoourshareholderswillbeatthediscretionofourboardofdirectors.Totheextentdistributionsaremadewithrespecttoourordinaryshares,

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subjecttothepassiveforeigninvestmentcompany,or"PFIC,"rulesdiscussedbelow,aU.S.Holderofordinarysharesgenerallywillberequiredtotreatdistributionsreceivedwithrespecttosuchordinaryshares(includinganyamountswithheldpursuanttoLuxembourgtaxlaw)asdividendincometotheextentofourcurrentoraccumulatedearningsandprofits(computedusingU.S.federalincometaxprinciples),withtheexcess(ifany)treatedasanon-taxablereturnofcapitaltotheextentoftheholder'sadjustedtaxbasisintheordinarysharesand,thereafter,ascapitalgain.However,wedonotmaintaincalculationsofourearningsandprofitsinaccordancewithU.S.federalincometaxaccountingprinciples.U.S.Holdersshouldthereforeassumethatdistributionswithrespecttoourordinaryshareswillconstituteordinarydividendincome.DividendspaidontheordinaryshareswillnotbeeligibleforthedividendsreceiveddeductionallowedtoU.S.corporations.

DividendspaidtoanoncorporateU.S.Holderbya"qualifiedforeigncorporation"maybesubjecttoreducedratesoftaxationifcertainholdingperiodandotherrequirementsaremet.Aqualifiedforeigncorporationgenerallyincludesaforeigncorporation(otherthanaPFIC)if(i)itsordinarysharesarereadilytradableonanestablishedsecuritiesmarketintheUnitedStatesor(ii)itiseligibleforbenefitsunderacomprehensiveU.S.incometaxtreatythatincludesanexchangeofinformationprogram.OurordinarysharesarereadilytradableontheNewYorkStockExchange.U.S.InternalRevenueService("IRS")guidanceindicatesthatordinaryshareslistedontheNewYorkStockExchangewillbereadilytradableforpurposesofsatisfyingtheconditionsrequiredforthesereducedtaxrates.U.S.Holdersshouldconsulttheirowntaxadvisorsregardingtheavailabilityofthereducedtaxrateondividendsinlightoftheirparticularcircumstances.

DistributionspaidinacurrencyotherthanU.S.dollarswillbeincludedinaU.S.Holder'sgrossincomeinaU.S.dollaramountbasedonthespotexchangerateineffectonthedateofactualorconstructivereceipt,whetherornotthepaymentisconvertedintoU.S.dollarsatthattime.TheU.S.HolderwillhaveataxbasisinsuchcurrencyequaltosuchU.S.dollaramount,andanygainorlossrecognizeduponasubsequentsaleorconversionoftheforeigncurrencyforadifferentU.S.dollaramountwillbeU.S.sourceordinaryincomeorloss.IfthedividendisconvertedintoU.S.dollarsonthedateofreceipt,aU.S.Holdergenerallyshouldnotberequiredtorecognizeforeigncurrencygainorlossinrespectofthedividendincome.

AU.S.Holderthatpays(whetherdirectlyorthroughwithholding)LuxembourgincometaxwithrespecttodividendspaidonourordinarysharesmaybeentitledtoreceiveeitheradeductionoraforeigntaxcreditforsuchLuxembourgincometaxpaid,ormaybeentitledtoareducedrateofwithholdingundertheapplicableincometaxconventionbetweenLuxembourgandtheUnitedStates,asdescribedbelowunder"LuxembourgTaxConsiderations—WithholdingTaxonDividends."AU.S.HolderthatreceivesdividendsfromwhichLuxembourgincometaxhasbeenwithheldwillberequiredtoincludethegrossamountofthedividendinincome,whichamountmayexceedtheamountofcashreceived.Complexlimitationsapplytotheforeigntaxcredit,includingthegenerallimitationthatthecreditcannotexceedtheproportionateshareofaU.S.Holder'sU.S.federalincometaxliabilitythatsuchU.S.Holder's"foreignsource"taxableincomebearstosuchU.S.Holder'sworldwidetaxableincome.Inapplyingthislimitation,aU.S.Holder'svariousitemsofincomeanddeductionmustbeclassified,undercomplexrules,aseither"foreignsource"or"U.S.source."Inaddition,thislimitationiscalculatedseparatelywithrespecttospecificcategoriesofincome.Dividendspaidbyusgenerallywillconstitute"foreignsource"incomeandgenerallywillbecategorizedas"passivecategoryincome."However,if50%ormoreofourstockistreatedasheldbyU.S.persons,wewillbetreatedasa"UnitedStates—ownedforeigncorporation,"inwhichcasedividendsmaybetreatedforforeigntaxcreditlimitationpurposesas"foreignsource"incometotheextentattributabletoournon-U.S.sourceearningsandprofitsandas"U.S.source"incometotheextentattributabletoourU.S.sourceearningsandprofits.Becausetheforeigntaxcreditrulesarecomplex,eachU.S.Holdershouldconsultitsowntaxadvisorregardingtheforeigntaxcreditrules.

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Sale or Disposition of Ordinary Shares

AU.S.HoldergenerallywillrecognizegainorlossonthetaxablesaleorexchangeoftheordinarysharesinanamountequaltothedifferencebetweentheU.S.dollaramountrealizedonsuchsaleorexchange(determinedinthecaseofsharessoldorexchangedforcurrenciesotherthanU.S.dollarsbyreferencetothespotexchangerateineffectonthedateofthesaleorexchangeor,iftheordinarysharessoldorexchangedaretradedonanestablishedsecuritiesmarketandtheU.S.Holderisacashbasistaxpayeroranelectingaccrualbasistaxpayer,thespotexchangerateineffectonthesettlementdate)andtheU.S.Holder'sadjustedtaxbasisintheordinarysharesdeterminedinU.S.dollars.TheinitialtaxbasisoftheordinarysharestoaU.S.HolderwillbetheU.S.Holder'sU.S.dollarpurchasepricefortheshares(determinedbyreferencetothespotexchangerateineffectonthedateofthepurchase,orifthesharespurchasedaretradedonanestablishedsecuritiesmarketandtheU.S.Holderisacashbasistaxpayeroranelectingaccrualbasistaxpayer,thespotexchangerateineffectonthesettlementdate).

AssumingwearenotaPFICandhavenotbeentreatedasaPFICduringyourholdingperiodforourordinaryshares,suchgainorlosswillbecapitalgainorlossandwillbelong-termgainorlossiftheordinaryshareshavebeenheldformorethanoneyear.Undercurrentlaw,long-termcapitalgainsgenerallyareeligibleforreducedratesoftaxation.Thedeductibilityofcapitallossesissubjecttolimitations.Capitalgainorloss,ifany,recognizedbyaU.S.HoldergenerallywillbetreatedasU.S.sourceincomeorlossforU.S.foreigntaxcreditpurposes.U.S.HoldersareencouragedtoconsulttheirowntaxadvisorsregardingtheavailabilityoftheU.S.foreigntaxcreditintheirparticularcircumstances.

Medicare Contribution Tax

Inadditiontothetaxconsequencesdescribedaboveunder"CashDividendsandOtherDistributions"and"SaleorDispositionofOrdinaryShares,"certainU.S.Holdersthatareindividuals,estatesortrustsaresubjecttoanadditional3.8%Medicarecontributiontaxonthelesserof(1)theU.S.Holder's"netinvestmentincome"fortherelevanttaxableyearand(2)theexcessoftheU.S.Holder'smodifiedadjustedgrossincomeforthetaxableyearoveracertainthreshold.Forthesepurposes,"netinvestmentincome"includes,amongotherthings,dividendson,andcapitalgainsfromthesaleorotherdispositionof,stock.U.S.Holdersareadvisedtoconsulttheirowntaxadvisorsregardingthepossibleimplicationsofthisadditionaltaxinlightoftheirparticularcircumstances.

Potential Application of Passive Foreign Investment Company Provisions

WedonotcurrentlyexpecttobetreatedasaPFICforU.S.federalincometaxpurposeswithrespecttoourtaxableyearendingDecember31,2016,andwedonotexpecttobetreatedasaPFICinthefuture.However,ouractualPFICstatusforanytaxableyearwillnotbedeterminableuntilthecloseofsuchyear,and,accordingly,thereisnoguaranteethatwewillnotbeaPFICforthecurrentoranyfuturetaxableyear.Anon-U.S.corporationisconsideredtobeaPFICforanytaxableyearifeither:

• atleast75%ofitsgrossincomeispassiveincome(the"incometest");or

• atleast50%ofthevalueofitsassets(basedonanaverageofthequarterlyvaluesoftheassetsduringataxableyear)isattributabletoassetsthatproduceorareheldfortheproductionofpassiveincome(the"assettest").

Forpurposesoftheabovetests,wewillbetreatedasowningourproportionateshareoftheassetsandearningourproportionateshareoftheincomeofanyothercorporationinwhichweown,directlyorindirectly,25%ormore(byvalue)ofthecorporation'sstock.Subjecttovariousexceptions,passiveincomegenerallyincludesdividends,interest,rents,royaltiesandgainsfromthedispositionofassetsthatproduceorareheldfortheproductionofpassiveincome.

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WemustmakeaseparatedeterminationeachyearastowhetherweareaPFIC.ThedeterminationofwhetherweareaPFICismadeannuallyanddependsontheparticularfactsandcircumstances(suchasthevaluationofourassets,includinggoodwillandotherintangibleassets)andalsomaybeaffectedbytheapplicationofthePFICrules,whicharesubjecttodifferinginterpretations.Thefairmarketvalueofourassetsisexpectedtodepend,inpart,upon(a)themarketpriceofourordinaryshares,whichislikelytofluctuate,and(b)thecompositionofourincomeandassets,whichwillbeaffectedbyhow,andhowquickly,wespendanycashthatisraisedinanyfinancingtransaction.Asaresult,ourPFICstatusmaychange.IfweareaPFICforanytaxableyearduringwhichaU.S.Holderholdsordinaryshares,wegenerallywillcontinuetobetreatedasaPFICforallsucceedingyearsduringwhichsuchU.S.Holderholdstheordinaryshares.However,ifweceasetobeaPFIC,aU.S.HoldermayavoidsomeoftheadverseeffectsofthePFICregimethereafterbymakinga"deemedsale"electionwithrespecttotheordinaryshares.

IfweareorbecomeaPFICinataxableyearinwhichwepayadividendorthepriortaxableyear,thereduceddividendratediscussedabovewithrespecttodividendspaidtonon-corporateholderswouldnotapply.Inaddition,ifweareaPFICforanytaxableyearduringwhichaU.S.Holderholdsordinaryshares,theU.S.Holderwillbesubjecttospecialtaxruleswithrespecttoany"excessdistribution"thattheU.S.HolderreceivesandanygaintheU.S.Holderrealizesfromasaleorotherdisposition(includingapledgeoradeemeddisposition)oftheordinaryshares,unlesstheU.S.Holdermakesa"mark-to-market"electionasdiscussedbelow.DistributionstheU.S.Holderreceivesinataxableyearthataregreaterthan125%oftheaverageannualdistributionstheU.S.HolderreceivedduringtheshorterofthethreeprecedingtaxableyearsortheU.S.Holder'sholdingperiodfortheordinaryshareswillbetreatedasexcessdistributions.Underthesespecialtaxrules:

• theexcessdistributionorgainfromasaleorotherdispositionwillbeallocatedratablyovertheU.S.Holder'sholdingperiodfortheordinaryshares;

• theamountallocatedtothecurrenttaxableyear,andanytaxableyearpriortothefirsttaxableyearinwhichtheCompanybecameaPFIC,willbetreatedasordinaryincome;and

• theamountallocatedtoeachotheryearwillbesubjecttothehighestapplicabletaxrateineffectfortheapplicablecategoryoftaxpayerforthattaxableyearandtheinterestchargegenerallyapplicabletounderpaymentsoftaxwillbeimposedontheresultingtaxattributabletoeachsuchyear.AU.S.Holderthatisnotacorporationwillberequiredtotreatanysuchinterestas"personalinterest,"whichisnotdeductible.

Thetaxliabilityforamountsallocatedtoyearspriortotheyearofdispositionor"excessdistribution"cannotbeoffsetbyanynetoperatinglossesforsuchyears,andgains(butnotlosses)realizedonthesaleoftheordinarysharescannotbetreatedascapital,evenifyouholdtheordinarysharesascapitalassets.Specialforeigntaxcreditrulesapplywithrespecttoexcessdistributions.Pleaseconsultyourowntaxadvisorwithrespecttosuchrules.

IfweareaPFICforanytaxableyearduringwhichaU.S.Holderholdsoursharesandanyofournon-U.S.subsidiariesisalsoaPFIC,aU.S.Holderwouldbetreatedasowningaproportionateamount(byvalue)ofthesharesofthelower-tierPFICforpurposesoftheapplicationoftheserules.Underthesecircumstances,aU.S.HolderwouldbesubjecttoU.S.federalincometaxon(i)adistributiononthesharesofalower-tierPFICand(ii)adispositionofsharesofalower-tierPFIC,bothasifsuchU.S.Holderdirectlyheldthesharesofsuchlower-tierPFIC.YouareurgedtoconsultyourowntaxadvisorsabouttheapplicationofthePFICrulestoanyofoursubsidiaries.

Alternatively,incertaincircumstances,aU.S.Holderof"marketablestock"(asdefinedbelow)ofaPFICmaymakeamark-to-marketelectionwithrespecttosuchstocktoelectoutoftheexcessdistributionregimediscussedabove.IfaU.S.Holdermakesavalidmark-to-marketelectionfortheordinarysharestheU.S.Holderwillincludeinincomeeachyearanamountequaltotheexcess,ifany,

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ofthefairmarketvalueoftheordinarysharesasofthecloseoftheU.S.Holder'staxableyearovertheU.S.Holder'sadjustedbasisinsuchordinaryshares.AU.S.Holderisallowedadeductionfortheexcess,ifany,oftheadjustedbasisoftheordinarysharesovertheirfairmarketvalueasofthecloseofthetaxableyear.However,deductionsareallowableonlytotheextentofanynetmark-to-marketgainsontheordinarysharesincludedinyourincomeforpriortaxableyears.AmountsincludedintheU.S.Holder'sincomeunderamark-to-marketelection,aswellasgainontheactualsaleorotherdispositionoftheordinaryshares,aretreatedasordinaryincome.Ordinarylosstreatmentalsoappliestothedeductibleportionofanymark-to-marketlossontheordinaryshares,aswellastoanylossrealizedontheactualsaleordispositionoftheordinaryshares,totheextentthattheamountofsuchlossdoesnotexceedthenetmark-to-marketgainspreviouslyincludedforsuchordinaryshares.TheU.S.Holder'sbasisintheordinaryshareswillbeadjustedtoreflectanysuchincomeorlossamounts.IfaU.S.Holdermakessuchanelection,thetaxrulesthatapplytodistributionsbycorporationsthatarenotPFICswouldapplytodistributionsbyus,exceptthatthereducedratediscussedaboveunder"—CashDividendsandOtherDistributions"wouldnotapply.IfaU.S.Holdermakesamark-to-marketelection,itwillbeeffectiveforthetaxableyearforwhichtheelectionismadeandallsubsequenttaxableyearsunlesstheordinarysharesarenolonger"marketablestock"(asdefinedbelow)ortheIRSconsentstotherevocationoftheelection.Amark-to-marketelectionwouldnotbeavailablewithrespecttoasubsidiaryPFICofoursthataU.S.HolderisdeemedtoownforthepurposesofthePFICrules;accordingly,aU.S.HolderwouldnotbeabletomitigatecertainoftheadverseU.S."excessdistribution"federalincometaxconsequencesofitsdeemedownershipofstockinoursubsidiaryPFICsbymakingamark-to-marketelection.U.S.Holdersareurgedtoconsulttheirowntaxadvisorsabouttheavailabilityofthemark-to-marketelectionandwhethermakingtheelectionwouldbeadvisableintheirparticularcircumstances.

Asdescribedabove,themark-to-marketelectionisavailableonlyfor"marketablestock,"whichisstockthatistradedinotherthandeminimisquantitiesonatleast15daysduringeachcalendarquarter("regularlytraded")onaqualifiedexchangeorothermarket,asdefinedinapplicableU.S.Treasuryregulations.TheNewYorkStockExchangeisaqualifiedexchange.Pleaseconsultyourowntaxadvisorwithrespecttosuchrules.

U.S.HolderswhoholdordinarysharesinanyyearinwhichweareaPFICwillberequiredtofileIRSForm8621regardinganydistributionsreceivedontheordinarysharesandanygainrealizedonthedispositionofsuchsharesandanannualinformationreturn(alsoonIRSForm8621)relatingtotheirownershipofourordinaryshares.Inaddition,otherreportingrequirementsmayapply.

Incertaincircumstances,holdersofPFICsharescanavoidtherulesdescribedabovebyelectingtotreatthePFICasa"qualifiedelectingfund"underSection1295oftheCode.However,becausewedonotintendtoprepareorprovidetheinformationthatwouldenableaU.S.Holdertomakeaqualifiedelectingfundelection,thisoptionwillnotbeavailabletoU.S.Holders.

YouareurgedtoconsultyourowntaxadvisorregardingtheapplicationofthePFICrulestoyourinvestmentinourordinaryshares.

Reporting Requirements and Backup Withholding

InformationreportingtotheIRSgenerallywillberequiredwithrespecttopaymentsontheordinarysharesandproceedsofthesaleoftheordinarysharespaidwithintheUnitedStatesorthroughcertainU.S.-relatedfinancialintermediariestoholdersthatareU.S.taxpayers,otherthanexemptrecipients.A"backup"withholdingtaxmayapplytothosepaymentsifsuchaholderfailstoprovideataxpayeridentificationnumbertothepayingagentandtocertifythatnolossofexemptionfrombackupwithholdinghasoccurred(orifsuchholderotherwisefailstoestablishanexemption).Weortheapplicablepayingagentwillwithholdonadistributionifrequiredbyapplicablelaw.Theamountswithheldunderthebackupwithholdingrulesarenotanadditionaltaxandmayberefunded,

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orcreditedagainsttheholder'sU.S.federalincometaxliability,ifany,providedtherequiredinformationistimelyfurnishedtotheIRS.

U.S.Holdersthatowncertain"foreignfinancialassets"(whichmayincludetheordinaryshares)arerequiredtoreportinformationrelatingtosuchassets,subjecttocertainexceptions,onIRSForm8938.Inadditiontotheserequirements,U.S.HoldersmayberequiredtoannuallyfileFinCENReport114,ReportofForeignBankandFinancialAccounts("FBAR")withtheU.S.DepartmentofTreasury.U.S.HoldersshouldconsulttheirowntaxadvisorsregardingtheapplicabilityofFBARandotherreportingrequirementsinlightoftheirindividualcircumstances.

THE ABOVE DISCUSSION DOES NOT COVER ALL TAX MATTERS THAT MAY BE OF IMPORTANCE TO A PARTICULAR INVESTOR.YOU ARE STRONGLY URGED TO CONSULT YOUR OWN TAX ADVISOR ABOUT THE TAX CONSEQUENCES TO YOU OF ANINVESTMENT IN THE ORDINARY SHARES.

Luxembourg Tax Considerations

The following is a general overview of certain important Luxembourg tax consequences that may be or become relevant in relation to a shareholder only andis presented by way of guidance only. It does not purport to be a complete summary of tax law and practice currently applicable in Luxembourg. Any potentialinvestor should consult its own tax advisor for more information about the tax consequences of acquiring, owning and disposing of the shares as it relates to theshareholder's particular circumstances. This taxation overview does not discuss every aspect of taxation that may be relevant to a particular purchaser underspecial circumstances or who is subject to special treatment under applicable law. This overview is based on Luxembourg tax law in force and applied inLuxembourg at the date of this prospectus. The laws upon which this overview is based may change. Any such changes could apply with retroactive effect andcould affect the continued validity of this overview.

Preliminary Consideration on the Luxembourg Tax Residency of the Company's Shareholders

Ashareholderwillnotbecomearesident,norbedeemedtobearesident,ofLuxembourg,bymerelyholdingtheshares,orbytheexecution,performance,deliveryand/orenforcementoftheshares.

Withholding Tax on Dividends

Totheextentthereareanydividendspaidwithrespecttoourordinaryshares,thesedividendsarenormallysubjecttowithholdingtaxinLuxembourgatthedomesticrateof15%,unless(i)thereducedwithholdingtaxratesasprovidedforbyrelevantdoubletaxationtreatiesapplyor,(ii)theconditionstobenefitfromtheexemptionofwithholdingtaxsetoutunderarticle147LuxembourgincometaxlawofDecember4,1967("LITL")aremet:

• onthedatethedistributionismadeavailabletoashareholder,therelevantshareholderholdsorcommitstoholddirectlyorthroughataxtransparentvehicle,duringanuninterruptedperiodofatleast12months,aparticipation(a)representingatleast10%ofthesharecapitaloftheCompany,or(b)havinganacquisitioncostofatleast€1.2million;and

• thebeneficiaryofthedividendsis:

• acompany("société à caractère collectif ")residentinLuxembourgfullyliabletoLuxembourgtax;

• anEUresidentcompanywithinthemeaningofarticle2oftheEUCouncilDirective90/435/ECofJuly23,1990concerningthecommonfiscalregimeapplicabletoparentandsubsidiarycompaniesofdifferentmemberstates("theParent-SubsidiaryDirective",tobereadwiththeCircularL.I.R.No.147/1ofMarch6,2012)oritsLuxembourgpermanentestablishment;or

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• aSwisscorporationwhichisliabletoSwisscorporatetaxwithoutbenefitingfromanexemption;

• acompanysubjecttoanincometaxationcomparabletotheLuxembourgcorporateincometax(inpracticeataxrateof10.5%appliedonacomparabletaxablebasisshouldbeacceptable),whichisresidentinacountryhavingadoubletaxationtreatywithLuxembourgoritsLuxembourgpermanentestablishment;

• acorporationoracooperativecompanyresidentinanon-EuropeanUnioncountrythatismemberoftheEEAthatisfullysubjecttoanincometaxationcorrespondingtotheLuxembourgcorporateincometax;or

• apermanentestablishmentofacorporationoracooperativecompanyresidentinanon-EuropeanUnioncountrymemberoftheEEA.

Withrespecttotheapplicationofthisexemption,Luxembourgtaxauthoritiestaketheviewthatthewithholdingtaxshouldbeappliedtoanydistributionsmadetoshareholdersholdingadirectparticipationofatleast10%(orhavinganacquisitioncostofatleastof€1.2million)beforethe12monthsperiodhaselapsed.Repaymentofthiswithholdingtaxcanultimatelyberequestedbytherelevantshareholder.

Acommonanti-abuserule(the"CAAR")wasintroducedintheParent-SubsidiaryDirectiveandwasimplementedbytheEUMemberStates,includingLuxembourg,intheirnationallaweffectiveonJanuary1,2016.Underthenewlaw,dividenddistributionsdonotbenefitfromthewithholdingtaxexemptionwhen(i)thebeneficiaryisanEUresidentcompanyorapermanentestablishmentinanotherEUMemberStateofacompanyresidentinaEUMemberStateand(ii)thedistributionsaremadeintheframeworkofanarrangementwhich,havingbeenputinplacewithwhereoneofthemainpurposesisobtainingataxadvantagethatdefeatstheobjectorpurposesoftheParent-SubsidiaryDirective,andisnotgenuineinlightofalltherelevantfactsandcircumstances.Anarrangementwillnotbeconsideredgenuinetotheextentitisnotputinplaceforvalideconomicreasonswhichreflecteconomicreality.

TotheextentawithholdingtaxappliestheCompanyisresponsibleforwithholdingtaxableamounts.

Capital Decrease

Thereimbursementofsharecapital,includingsharepremium,bytheCompanyisnottreatedasadividenddistributionforLuxembourgwithholdingtaxpurposesandthusnotsubjecttoanywithholdingtax,provided(i)therearenoreservesorprofitsattheCompanylevel,and(ii)thecapitaldecreaseismotivatedbysoundbusinessreasons.IncasetheCompanydoesnothavesoundbusinessreasonstoproceedtoacapitaldecrease,theentireamountpaidwillbesubjecttoa15%withholdingtax,unlesstheconditionsforanexemptionorareductionfromthewithholdingtaxondividendssetforthabovearemet.

Arepurchaseofshareswithanimmediatecancellationofthesharesfollowsinprinciplethesametaxtreatmentasareimbursementofsharecapital.However,insuchacase,iftheshareholderceasestobeashareholder,thereimbursementwillnotbesubjecttoawithholdingtax.Incasethesharesarenotimmediatelycancelled,arepurchaseofsharesmaybetreatedforLuxembourgtaxpurposesasadividenddistribution.

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Income Taxation of Luxembourg Resident Shareholders

Luxembourg Resident Individuals

50%ofthedividendsreceivedbyresidentindividuals,whoactinthecourseofeithertheirprivatewealthortheirprofessional/businessactivities,aresubjecttoincometaxattheprogressiveordinaryrate(withthemaximumeffectivemarginaltaxratebeingat42.8%or43.6%dependingontheamountoftaxableincome).Theother50%ofthedividendsreceivedaretax-exempt.The15%withholdingtaxmaybeoffsetagainstthisincometaxliability.

Againrealizeduponthesale,disposalorredemption(however,inthecaseofapartialredemptionthetaxtreatmentappliedwillbethesameasfordividends)ofsharesbyLuxembourgresidentindividualshareholders,actinginthecourseofthemanagementoftheirprivatewealthisnotsubjecttoLuxembourgincometax,providedthissale,disposalorredemptiontookplacemorethan6monthsaftertheshareswereacquiredandprovidedthesharesdonotrepresentasubstantialshareholding.Ashareholdingisconsideredasubstantialshareholdinginlimitedcases,inparticularif(i)therelevantshareholderhasheld,eitheraloneortogetherwithitsspouseorpartnerand/oritsminorchildren,eitherdirectlyorindirectly,atanytimewithinthefiveyearsprecedingtherealizationofthegain,morethan10%ofthesharecapitaloftheCompany,or(ii)thetaxpayeracquiredfreeofcharge,withinthe5yearsprecedingthetransfer,aparticipationthatconstitutedasubstantialparticipationinthehandsofthealienator(orthealienatorsincaseofsuccessivetransfersfreeofchargewithinthesamefive-yearperiod).Capitalgainsrealizedonasubstantialparticipationmorethan6monthsaftertheacquisitionthereofaresubjecttoincometaxaccordingtothehalf-globalratemethod(i.e.,theaveragerateapplicabletothetotalincomeiscalculatedaccordingtoprogressiveincometaxratesandhalfoftheaveragerateisappliedtothecapitalgainsrealizedonthesubstantialparticipation).Adisposalmayincludeasale,anexchange,acontributionoranyotherkindofalienationoftheshareholding.Capitalgainsrealizedonthedisposalofthesharesbyresidentindividualholders,whoactinthecourseoftheirprofessionalorbusinessactivities,aresubjecttoincometaxatordinaryrates.Taxablegainsaredeterminedasbeingthedifferencebetweenthepriceforwhichtheshareshavebeendisposedofandtheloweroftheircostorbookvalue.

50%ofthedividendsreceivedbyresidentindividuals,whoactinthecourseoftheirprofessionalandbusinessactivities,aresubjecttothemunicipalbusinesstax("MBT")ataratedependingonthemunicipalitywhichvariesfrom6%to10.5%.However,forresidentindividuals,MBTisfullytaxdeductible.

Luxembourg Corporate Residents

Luxembourgresidentcorporateshareholders(société à caractère collectif )oftheCompanymustinclude50%ofthedividendsreceivedandanycapitalgainsderivedfromtheshares,intheirtaxableprofitsforLuxembourgincometaxassessmentpurposes(corporateincometax("CIT")andMBTatthemaximumaggregaterateof29.2%in2016forcorporateshareholdershavingtheirstatutoryseatinLuxembourgCity).Theother50%ofthedividendsreceivedaretaxexempt.The15%withholdingtaxmaybeoffsetagainsttheincometaxliability.Taxablegainsaredeterminedasbeingthedifferencebetweenthesale,repurchaseorredemptionpriceandthelowerofthecostorbookvalueofthesharessoldorredeemed.

However,dividendsandliquidationproceedsreceivedbyLuxembourgresidentcorporateshareholdersfromtheCompanywillbeexemptfromCITandMBTincaseofaparticipationhelddirectly,orindirectlythroughataxtransparentvehicle,representingatleast10%ofthesharecapitaloftheCompanyoranacquisitionpriceofatleast€1.2million,providedthatatthetimeoftheincomeismadeavailable,therecipienthasheldorcommitstoholdtheparticipationduringanuninterruptedperiodofatleasttwelvemonths.

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CapitalgainsrealizedupondisposalofthesharesbyaLuxembourgresidentcorporateshareholderwillbeexemptedincaseofaparticipationhelddirectly,orindirectlythroughataxtransparentvehicle,representingatleast10%ofthesharecapitaloftheCompanyoranacquisitionpriceofatleast€6million,providedthatatthetimeofthedisposal,thebeneficiaryhasheldorcommitstoholdtheparticipationduringanuninterruptedperiodofatleasttwelvemonths.

Luxembourg Residents Benefiting from a Special Tax Regime

LuxembourgresidentshareholdersoftheCompanythatareentitiesbenefitingfromaspecialtaxregime,suchas,(i)undertakingsforcollectiveinvestmentsubjecttotheamendedlawofDecember17,2010(Loi du 17 décembre 2010 concernant les sociétés de placement ),(ii)specializedinvestmentfundssubjecttotheamendedlawofFebruary13,2007(Loi du 13 février 2007 relative aux fonds d'investissement spécialisés ),or(iii)familywealthmanagementcompaniesgovernedbytheamendedlawofMay11,2007(Loi du 11 mai 2007 relative à la création une société de gestion de patrimoine familial (SPF) )aretaxexemptentitiesinLuxembourgandarethusnotsubjecttoanyLuxembourgincometax.

Income Taxation of Luxembourg Non-resident Shareholders

ShareholdersoftheCompanywhoarenon-residentsofLuxembourgandwhohaveneitherapermanentestablishmentnorapermanentrepresentativeinLuxembourgtowhichortowhomthesharesareattributable,aregenerallynotliabletoanyLuxembourgincometax.

Asanexception,anon-residentshareholdermaybeliabletoLuxembourgincometaxoncapitalgainsrealizedonthesharesifithasheld,eitheraloneortogetherwithitsspouseorpartnerand/oritsminorchildren,directlyorindirectly,atanytimewithinthefiveyearsprecedingthedisposaloftheshares,morethan10%ofthesharesoftheCompanyandithaseither(i)heldthesharesforlessthan6months,or(ii)beenaLuxembourgresidenttaxpayerformorethan15yearsandbecameanon-residentlessthanfiveyearsbeforetherealizationofthecapitalgainsontheshares.Dependingontheshareholder'sresidence,suchnon-residentshareholdersmight,however,claimtaxtreatybenefitsinordertoavoidLuxembourgtaxonanysuchcapitalgains.

Non-residentcorporateshareholdersthathaveapermanentestablishmentorapermanentrepresentativeinLuxembourgtowhichorwhomthesharesareattributable,mustincludeanyincomereceived,aswellasanygainrealizedonthesale,disposalorredemptionofshares,intheirtaxableincomeforLuxembourgtaxassessmentpurposes.Thesameinclusionappliestoindividuals,actinginthecourseofthemanagementofaprofessionalorbusinessundertaking,whohaveapermanentestablishmentorapermanentrepresentativeinLuxembourgtowhichorwhomthesharesareattributable.Taxablegainsaredeterminedasbeingthedifferencebetweenthesale,repurchase,orredemptionpriceandthelowerofthecostorbookvalueofthesharessoldorredeemed.

Net Wealth Tax

LuxembourgresidentshareholdersandshareholderswhohaveapermanentestablishmentorapermanentrepresentativeinLuxembourgtowhichorwhomthesharesareattributablearesubjecttoLuxembourgnetwealthtax("NWT")onsuchshares,exceptifsuchshareholderis(i)aresidentornon-residentindividualtaxpayer,(ii)anundertakingforcollectiveinvestmentsubjecttotheamendedlawofDecember17,2010(Loi du 17 décembre 2010 concernant les sociétés deplacement collectif ),(iii)asecuritizationcompanygovernedbytheamendedlawofMarch22,2004onsecuritization(Loi du 22 mars 2004 relative à latitrisation ),(iv)acompanygovernedbytheamendedlawofJune15,2004onventurecapitalvehicles(Loi du 15 juin 2004 relative à la Société d'investissementen capital à risque (SICAR) ),(v)aspecializedinvestmentfundgovernedbytheamendedlawofFebruary13,2007(Loi du 13 février 2007 relative aux fondsd'investissement spécialisés ),(vi)afamilywealthmanagementcompanygovernedbytheamendedlawofMay11,2007(Loi du 11 mai 2007 relative à lacréation d'une

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société de gestion de patrimoine familial (SPF) ),or(vii)aresidentcorporateshareholderwhoholdsaparticipationdirectly,orindirectlythroughataxtransparentvehicle,representingatleast10%ofthesharecapitaloftheCompanyoranacquisitionpriceofatleast€1.2million.However,iftheshareholderisavehiclelistedaboveunder(iii),(iv)or(vii),asfrom1January2016,itmightbesubject(a)toaminimumnetwealthtaxofEUR3,210,ifitholdsassetssuchasfixedfinancialassets,receivablesowedtoaffiliatedcompanies,transferablesecurities,postalcheckingaccounts,checksandcash,inaproportionthatexceeds90%ofitstotalbalancesheetvalueandifthetotalbalancesheetvalueexceedsEUR350,000or(b)toaminimumnetwealthtaxbetweenEUR535andEUR32,100basedonthetotalamountofitsassets.

Other Taxes

NoLuxembourgvalueaddedtax,Luxembourgregistrationduties,orsimilartaxesareleviedonthetransferoftheshares.

NoestateorinheritancetaxisleviedonthetransferofthesharesupondeathofashareholderoftheCompanyincaseswherethedeceasedwasnotaresidentofLuxembourgforinheritancetaxpurposes.

LuxembourgtaxmaybeleviedonagiftordonationofthesharesifembodiedinaLuxembourgnotarialdeedorotherwiseregisteredinLuxembourg.WhereashareholderisaresidentofLuxembourgfortaxpurposesatthetimeofhisdeath,thesharesareincludedinitstaxableestateforinheritancetaxorestatetaxpurposes.

Foreign Account Tax Compliance Act (FATCA) Requirements

FATCArequiresfinancialinstitutionstoreportonanannualbasistotheIRScertaininformationonU.S.personsthatholdaccountsoutsidetheU.S.,asasafeguardagainstU.S.taxevasion.Inaddition,FATCAgenerallyimposesa30%withholdingtaxoncertainU.S.sourcepayments(includingdividendsandgrossproceedsfromthesaleorotherdisposalofpropertythatcanproduceU.S.sourceincome)whenmadetoanindividualorentitythatdoesnotcomplywithFATCAprovisions.UnderapplicableU.S.TreasuryRegulations,withholdingpursuanttoFATCAwithrespecttogrossproceedswillapplyonlyafterJanuary1,2019.The30%withholdingcouldalsoapplytopaymentsotherwiseattributabletoU.S.sourceincome(alsoknownas"foreignpass-throughpayments").

OnMarch28,2014,theU.S.andtheGrandDuchyofLuxembourgsignedanintergovernmentalagreement(IGA)intheformofModel1,whichrequiresLuxembourgfinancialinstitutionstoreportallFATCA-relatedinformationtotheirowngovernmentalagencies,whichwouldthenreportsuchinformationtotheIRS.TheIGAhasbeenimplementedinLuxembourgbyalawdatedJuly24,2015.

InvestorsshouldconsulttheirowntaxadvisorsregardingtheFATCArequirementswithrespecttotheirownsituationontheirinvestmentintheCompany.Inparticular,investorswhoholdtheirinvestmentthroughintermediariesshouldconfirmtheFATCAcompliancestatusofthoseintermediariestoensurethattheydonotsufferU.S.withholdingtaxontheirinvestmentreturns.

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SELLING SHAREHOLDER

ThefollowingtablesetsforthinformationregardingthebeneficialownershipofourordinarysharesasofSeptember6,2016,andasadjustedtogiveeffecttotheofferingbythesellingshareholder.

Thepercentageofbeneficialownershipiscalculatedbasedon45,145,431ordinarysharesoutstandingasofSeptember6,2016,excludingtreasuryshares,andthenumberofunissuedsharesastowhichsuchsellingshareholderhastherighttoacquirevotingand/orinvestmentpowerwithin60days.Thebeneficialownershipinformationsetforthbelowwasprovidedbyoronbehalfofthesellingshareholder,andwehavenotindependentlyverifiedtheaccuracyorcompletenessoftheinformationsoprovided.

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Shares Owned Before the Offering

Shares Owned After the Offering

Shares Offered Hereby

Name of Selling Shareholder Number Percentage Number Percentage BainCapitalEverestManagerHoldingSCA(1) 10,669,567 23.6% 10,669,567 — —

(1) ThegeneralpartnerofourParentisBainCapitalEverestManagerS.à.r.l.("BCEM").Byvirtueoftherelationshipsdescribedinthisfootnote,BCEMmaybedeemedtoexercisevotinganddispositivepowerwithrespecttothesharesheldbyParent.MichelG.Plantevin,AurélienVasseur,ChristopherD.Pappas,StephenThomas,FelixHauser,andStephenM.ZideareeachmanagersofBCEM.ThemanagersofBCEMdisclaimbeneficialownershipofsuchsharestotheextentattributedtothemsolelybyvirtueofservingasamanagerofBCEM.AlloftheoutstandingsharecapitalofBCEMisheldbyBainCapitalEuropeFundIII,L.P.("EuropeFundIII")and,inthatcapacity,EuropeFundIIIhasthepowertoappointthemanagersofBCEM.BainCapitalInvestors,LLC("BCI")isthegeneralpartnerofBainCapitalPartnersEuropeIII,L.P.,whichisthegeneralpartnerofEuropeFundIII.Asaresultoftherelationshipsdescribedabove,BCImaybedeemedtosharebeneficialownershipofthesharesheldbyourParent.Thegovernance,investmentstrategyanddecision-makingprocesswithrespecttoinvestmentsheldbyEuropeFundIIIisdirectedbyBCI'sGlobalPrivateEquityBoard("GPEB"),whichiscomprisedofthefollowingindividuals:StevenBarnes,JoshuaBekenstein,JohnConnaughton,DavidGross-Loh,StephenPagliuca,MichelG.Plantevin,DwightPoler,andJonathanZhu.Byvirtueoftherelationshipsdescribedinthisfootnote,GPEBmaybedeemedtoexercisevotinganddispositivepowerwithrespecttothesharesheldbyourParent.EachofthemembersofGPEBdisclaimsbeneficialownershipofsuchsharestotheextentattributedtosuchmembersolelybyvirtueofservingonGPEB.TheaddressforourParentandBCEMis4,rueLouHemmer,L-1748Luxembourg,GrandDuchyofLuxembourg.EuropeFundIIIhasanaddressofUglandHouse,SouthChurchStreet,GeorgeTown,GrandCayman,KY1-1104CaymanIslandsandBCIhasanaddressc/oBainCapitalPrivateEquity,LP,200ClarendonStreet,Boston,Massachusetts02116.TheaddressofMr.Hauserisc/oBainCapitalBeteiligungsberatungGmbHMaximilianstrasse11,80539Munich,Germany.

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UNDERWRITING

MorganStanley&Co.LLCisactingastheunderwriterinconnectionwiththisoffering.SubjecttothetermsandconditionssetforthinanunderwritingagreementamongtheCompany,thesellingshareholderandtheunderwriter,theunderwriterhasagreedtopurchase10,669,567ordinarysharesfromthesellingshareholderatapriceof$pershare,whichwillresultin$ofproceedstothesellingshareholderbeforeexpenses.

Theunderwritermayreceivefrompurchasersofthesharesnormalbrokeragecommissionsinamountsagreedwithsuchpurchasers.TheunderwriterproposestooffertheordinarysharesforsalefromtimetotimeinoneormoretransactionsontheNewYorkStockExchange,intheover-the-countermarket,throughnegotiatedtransactionsorotherwiseatmarketpricesprevailingatthetimeofsale,atpricesrelatedtoprevailingmarketpricesoratnegotiatedprices,subjecttoreceiptandacceptancebytheunderwriterandsubjecttoitsrighttorejectanyorderinwholeorinpart.Theunderwritermayeffectsuchtransactionsbysellingordinarysharestoorthroughdealers,andsuchdealersmayreceivecompensationintheformofdiscounts,concessionsorcommissionsfromtheunderwriterand/orpurchasersofordinarysharesforwhomtheymayactasagentsortowhomtheymaysellasprincipals.Thedifferencebetweenthepriceatwhichtheunderwriterpurchasesordinarysharesandthepriceatwhichtheunderwriterresellssuchordinarysharesmaybedeemedunderwritingcompensation.Theunderwriteriscommittedtotakeandpayforallofthesharesbeingoffered,ifanyaretaken.

Theexpensesoftheofferingareestimatedatapproximately$300,000andarepayablebyus.Thesellingshareholderwillnotpayanyofferingexpenses.WehaveagreedwiththeunderwritertopayactualaccountablelegalfeesandfilingfeesandotherreasonabledisbursementsofcounseltotheunderwriterrelatingtothereviewandqualificationofthisofferingbytheFinancialIndustryRegulatoryAuthority,Inc.inanaggregateamountnottoexceed$30,000.

Inconnectionwiththisoffering,weandeachofourdirectorsandexecutiveofficershaveagreed,subjecttocertainexceptions,that,foraperiodof30daysafterthedateofthisprospectussupplement,weandtheywillnot,withoutthepriorwrittenconsentofMorganStanley&Co.LLC,directlyorindirectlyissue,sell,offer,pledgeorcontracttosell,grantanyoption,rightorwarrantforthesaleof,lendorotherwisetransferordisposeof,anyordinaryshares(otherthanthesharesofferedpursuanttothisoffering)oranysecuritiesconvertibleinto,orexercisableorexchangeablefor,ordinaryshares,includingthefiling(orparticipationinthefiling)ofaregistrationstatementwiththeSECinrespectof,ortheestablishmentorincreaseofaputequivalentpositionortheliquidationordecreaseofacallequivalentpositionwithinthemeaningofSection16oftheExchangeActwithrespectto,anyordinarysharesoranysecuritiesconvertibleinto,orexercisableorexchangeablefor,ordinaryshares;orpubliclyannounceanintentiontoeffectanysuchtransaction.

OurordinarysharesarelistedontheNYSEunderthesymbol"TSE."

Inconnectionwiththeoffering,theunderwritermaypurchaseandsellsharesintheopenmarket.Thesetransactionsmayincludeshortsales,stabilizingtransactionsandpurchasestocoverpositionscreatedbyshortsales.Shortsalesinvolvethesalebytheunderwriterofagreaternumberofsharesthanitisrequiredtopurchaseintheoffering,andashortpositionrepresentstheamountofsuchsalesthathavenotbeencoveredbysubsequentpurchases.Theunderwritermaycoveranycoveredshortpositionbypurchasingsharesintheopenmarket.Stabilizingtransactionsconsistofvariousbidsfororpurchasesofsharesmadebytheunderwriterintheopenmarketpriortothecompletionoftheoffering.

Purchasestocoverashortpositionandstabilizingtransactions,aswellasotherpurchasesbytheunderwriterforitsownaccounts,mayhavetheeffectofpreventingorretardingadeclineinthemarketpriceofthesharesandmaystabilize,togetherwiththeimpositionofthepenaltybid,maintainor

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otherwiseaffectthemarketpriceoftheshares.Asaresult,thepriceofthesharesmaybehigherthanthepricethatotherwisemightexistintheopenmarket.Theunderwriterisnotrequiredtoengageintheseactivitiesandmayendanyoftheseactivitiesatanytime.ThesetransactionsmaybeeffectedonNYSE,intheover-the-countermarketorotherwise.

Aprospectusinelectronicformatmaybemadeavailableonthewebsitesmaintainedbytheunderwriter.Theunderwritermayagreetoallocateanumberofourordinarysharesforsaletoitsonlinebrokerageaccountholders.TheunderwritermaymakeInternetdistributionsonthesamebasisasotherallocations.Inaddition,ourordinarysharesmaybesoldbytheunderwritertosecuritiesdealerswhoresellsuchsharestoonlinebrokerageaccountholders.Otherthantheprospectusinelectronicformat,theinformationontheunderwriter'sorthesellingshareholder'swebsiteandanyinformationcontainedinanyotherwebsitemaintainedbytheunderwriterisnotpartoftheprospectusortheregistrationstatementofwhichthisprospectussupplementformsapart,hasnotbeenapprovedorendorsedbyusortheunderwriterorthesellingshareholderinitscapacityasunderwriterorthesellingshareholderandshouldnotberelieduponbyinvestors.

Theunderwriteranditsaffiliateshaveengagedin,andmayinthefutureengagein,investmentbankingandothercommercialdealingsintheordinarycourseofbusinesswithusorouraffiliates.Theyhavereceived,ormayinthefuturereceive,customaryfeesandcommissionsforthesetransactions.

Inaddition,intheordinarycourseoftheirbusinessactivities,theunderwriteranditsaffiliatesmaymakeorholdabroadarrayofinvestmentsandactivelytradedebtandequitysecurities(orrelatedderivativesecurities)andfinancialinstruments(includingbankloans)fortheirownaccountandfortheaccountsoftheircustomers.Suchinvestmentsandsecuritiesactivitiesmayinvolvesecuritiesand/orinstrumentsofoursorouraffiliates.Theunderwriteranditsaffiliatesmayalsomakeinvestmentrecommendationsand/orpublishorexpressindependentresearchviewsinrespectofsuchsecuritiesorfinancialinstrumentsandmayhold,orrecommendtoclientsthattheyacquire,longand/orshortpositionsinsuchsecuritiesandinstruments.

OtherthanintheUnitedStates,noactionhasbeentakenbyusortheunderwriterthatwouldpermitapublicofferingoftheordinarysharesofferedbythisprospectussupplementinanyjurisdictionwhereactionforthatpurposeisrequired.Ordinarysharesofferedbythisprospectussupplementmaynotbeofferedorsold,directlyorindirectly,normaythisprospectussupplementoranyotherofferingmaterialoradvertisementsinconnectionwiththeofferandsaleofanysuchordinarysharesbedistributedorpublishedinanyjurisdiction,exceptundercircumstancesthatwillresultincompliancewiththeapplicablerulesandregulationsofthatjurisdiction.Personsintowhosepossessionthisprospectussupplementcomesareadvisedtoinformthemselvesaboutandtoobserveanyrestrictionsrelatingtothisofferingandthedistributionofthisprospectussupplement.Thisprospectussupplementdoesnotconstituteanoffertosellorasolicitationofanoffertobuyanyordinarysharesofferedbythisprospectussupplementinanyjurisdictioninwhichsuchanofferorasolicitationisunlawful.

Canada

Theordinarysharesofferedherebymaybesoldonlytopurchaserspurchasing,ordeemedtobepurchasing,asprincipalthatareaccreditedinvestors,asdefinedinNationalInstrument45-106ProspectusExemptionsorsubsection73.3(1)oftheSecuritiesAct(Ontario),andarepermittedclients,asdefinedinNationalInstrument31-103RegistrationRequirements,ExemptionsandOngoingRegistrantObligations.Anyresaleoftheordinarysharesofferedherebymustbemadeinaccordancewithanexemptionfrom,orinatransactionnotsubjectto,theprospectusrequirementsofapplicablesecuritieslaws.

SecuritieslegislationincertainprovincesorterritoriesofCanadamayprovideapurchaserwithremediesforrescissionordamagesifthisprospectussupplement(includinganyamendmentthereto)containsamisrepresentation,providedthattheremediesforrescissionordamagesareexercisedbythe

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purchaserwithinthetimelimitprescribedbythesecuritieslegislationofthepurchaser'sprovinceorterritory.Thepurchasershouldrefertoanyapplicableprovisionsofthesecuritieslegislationofthepurchaser'sprovinceorterritoryforparticularsoftheserightsorconsultwithalegaladvisor.

Pursuanttosection3A.3ofNationalInstrument33-105UnderwritingConflicts(NI33-105),theunderwriterisnotrequiredtocomplywiththedisclosurerequirementsofNI33-105regardingunderwriterconflictsofinterestinconnectionwiththisoffering.

European Economic Area

InrelationtoeachMemberStateoftheEuropeanEconomicAreawhichhasimplementedtheProspectusDirective(each,a"RelevantMemberState"),theunderwriterhasrepresentedandagreedthatwitheffectfromandincludingthedateonwhichtheProspectusDirectiveisimplementedinthatRelevantMemberState(the"RelevantImplementationDate")ithasnotmadeandwillnotmakeanofferofsharestothepublicinthatRelevantMemberStatepriortothepublicationofaprospectusinrelationtotheshareswhichhasbeenapprovedbythecompetentauthorityinthatRelevantMemberStateor,whereappropriate,approvedinanotherRelevantMemberStateandnotifiedtothecompetentauthorityinthatRelevantMemberState,allinaccordancewiththeProspectusDirective,exceptthatitmay,witheffectfromandincludingtheRelevantImplementationDate,makeanofferofsharestothepublicinthatRelevantMemberStateatanytime:

(a)toanylegalentitywhichisaqualifiedinvestorasdefinedintheProspectusDirective;

(b)tofewerthan100or,iftheRelevantMemberStatehasimplementedtherelevantprovisionofthe2010PDAmendingDirective,150naturalorlegalpersons(otherthanqualifiedinvestors,asdefinedintheProspectusDirective)subjecttoobtainingthepriorconsentoftherepresentativesforanysuchoffer;or

(c)inanyothercircumstanceswhichdonotrequirethepublicationbyusofaprospectuspursuanttoArticle3oftheProspectusDirective.

Forthepurposesofthisprovision,theexpressionan"offerofsharestothepublic"inrelationtoanysharesinanyRelevantMemberStatemeansthecommunicationinanyformandbyanymeansofsufficientinformationonthetermsfortheofferandthesharestobeofferedsoastoenableaninvestortodecidetopurchaseorsubscribetheshares,asthesamemaybevariedinthatRelevantMemberStatebyanymeasureimplementingtheProspectusDirectiveinthatRelevantMemberState,theexpressionProspectusDirectivemeansDirective2003/71/EC(andamendmentsthereto,includingthePD2010AmendingDirectivetotheextentimplementedintheRelevantMemberState)andincludesanyrelevantimplementingmeasureineachRelevantMemberState,andtheexpression2010PDAmendingDirectivemeansDirective2010/73/EU.

United Kingdom

Thisprospectusandanyothermaterialinrelationtothesharesdescribedhereinisonlybeingdistributedto,andisonlydirectedat,personsintheUnitedKingdomthatarequalifiedinvestorswithinthemeaningofArticle2(1)(e)oftheProspectiveDirective("qualifiedinvestors")thatalso(i)haveprofessionalexperienceinmattersrelatingtoinvestmentsfallingwithinArticle19(5)oftheFinancialServicesandMarketsAct2000(FinancialPromotion)Order2005,asamended,ortheOrder,(ii)whofallwithinArticle49(2)(a)to(d)oftheOrderor(iii)towhomitmayotherwiselawfullybecommunicated(allsuchpersonstogetherbeingreferredtoas"relevantpersons").Thesharesareonlyavailableto,andanyinvitation,offeroragreementtopurchaseorotherwiseacquiresuchshareswillbeengagedinonlywith,relevantpersons.Thisprospectusanditscontentsareconfidentialandshouldnotbedistributed,publishedorreproduced(inwholeorinpart)ordisclosedbyrecipientstoanyother

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personintheUnitedKingdom.AnypersonintheUnitedKingdomthatisnotarelevantpersonshouldnotactorrelyonthisprospectusoranyofitscontents.

Switzerland

ThesharesmaynotbepubliclyofferedinSwitzerlandandwillnotbelistedontheSIXSwissExchange(the"SIX")oronanyotherstockexchangeorregulatedtradingfacilityinSwitzerland.Thisdocumenthasbeenpreparedwithoutregardtothedisclosurestandardsforissuanceprospectusesunderart.652aorart.1156oftheSwissCodeofObligationsorthedisclosurestandardsforlistingprospectusesunderart.27ff.oftheSIXListingRulesorthelistingrulesofanyotherstockexchangeorregulatedtradingfacilityinSwitzerland.NeitherthisdocumentnoranyotherofferingormarketingmaterialrelatingtothesharesortheofferingmaybepubliclydistributedorotherwisemadepubliclyavailableinSwitzerland.

Neitherthisprospectusnoranyotherofferingormarketingmaterialrelatingtotheoffering,theissuer,ortheshareshavebeenorwillbefiledwithorapprovedbyanySwissregulatoryauthority.Inparticular,thisprospectuswillnotbefiledwith,andtheofferofshareswillnotbesupervisedby,theSwissFinancialMarketSupervisoryAuthorityFINMA(the"FINMA"),andtheofferofshareshasnotbeenandwillnotbeauthorizedundertheSwissFederalActonCollectiveInvestmentSchemes(the"CISA").TheinvestorprotectionaffordedtoacquirersofinterestsincollectiveinvestmentschemesundertheCISAdoesnotextendtoacquirersofshares.

The Dubai International Financial Center

ThisprospectusrelatestoanExemptOfferinaccordancewiththeOfferedSecuritiesRulesoftheDubaiFinancialServicesAuthority(the"DFSA").ThisprospectusisintendedfordistributiononlytopersonsofatypespecifiedintheOfferedSecuritiesRulesoftheDFSA.Itmustnotbedeliveredto,orreliedonby,anyotherperson.TheDFSAhasnoresponsibilityforreviewingorverifyinganydocumentsinconnectionwithExemptOffers.TheDFSAhasnotapprovedthisprospectusnortakenstepstoverifytheinformationsetforthhereinandhasnoresponsibilityforthisprospectus.Thesharestowhichthisprospectusrelatesmaybeilliquidand/orsubjecttorestrictionsontheirresale.Prospectivepurchasersofthesharesofferedshouldconducttheirownduediligenceontheshares.Ifyoudonotunderstandthecontentsofthisprospectusyoushouldconsultanauthorizedfinancialadvisor.

Hong Kong

Thesharesmaynotbeofferedorsoldbymeansofanydocumentotherthan(i)incircumstanceswhichdonotconstituteanoffertothepublicwithinthemeaningoftheCompaniesOrdinance(Cap.32,LawsofHongKong),or(ii)to"professionalinvestors"withinthemeaningoftheSecuritiesandFuturesOrdinance(Cap.571,LawsofHongKong)andanyrulesmadethereunder,or(iii)inothercircumstanceswhichdonotresultinthedocumentbeinga"prospectus"withinthemeaningoftheCompaniesOrdinance(Cap.32,LawsofHongKong),andnoadvertisement,invitationordocumentrelatingtothesharesmaybeissuedormaybeinthepossessionofanypersonforthepurposeofissue(ineachcasewhetherinHongKongorelsewhere),whichisdirectedat,orthecontentsofwhicharelikelytobeaccessedorreadby,thepublicinHongKong(exceptifpermittedtodosounderthelawsofHongKong)otherthanwithrespecttoshareswhichareorareintendedtobedisposedofonlytopersonsoutsideHongKongoronlyto"professionalinvestors"withinthemeaningoftheSecuritiesandFuturesOrdinance(Cap.571,LawsofHongKong)andanyrulesmadethereunder.

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Singapore

ThisprospectushasnotbeenregisteredasaprospectuswiththeMonetaryAuthorityofSingapore.Accordingly,thisprospectusandanyotherdocumentormaterialinconnectionwiththeofferorsale,orinvitationforsubscriptionorpurchase,ofthesharesmaynotbecirculatedordistributed,normaythesharesbeofferedorsold,orbemadethesubjectofaninvitationforsubscriptionorpurchase,whetherdirectlyorindirectly,topersonsinSingaporeotherthan(i)toaninstitutionalinvestorunderSection274oftheSecuritiesandFuturesAct,Chapter289ofSingapore(the"SFA"),(ii)toarelevantperson,oranypersonpursuanttoSection275(1A),andinaccordancewiththeconditions,specifiedinSection275oftheSFAor(iii)otherwisepursuantto,andinaccordancewiththeconditionsof,anyotherapplicableprovisionoftheSFA.

WherethesharesaresubscribedorpurchasedunderSection275byarelevantpersonwhichis:(a)acorporation(whichisnotanaccreditedinvestor)thesolebusinessofwhichistoholdinvestmentsandtheentiresharecapitalofwhichisownedbyoneormoreindividuals,eachofwhomisanaccreditedinvestor;or(b)atrust(wherethetrusteeisnotanaccreditedinvestor)whosesolepurposeistoholdinvestmentsandeachbeneficiaryisanaccreditedinvestor,shares,debenturesandunitsofsharesanddebenturesofthatcorporationorthebeneficiaries'rightsandinterestinthattrustshallnotbetransferableforsixmonthsafterthatcorporationorthattrusthasacquiredthesharesunderSection275except:(1)toaninstitutionalinvestorunderSection274oftheSFAortoarelevantperson,oranypersonpursuanttoSection275(1A),andinaccordancewiththeconditions,specifiedinSection275oftheSFA;(2)wherenoconsiderationisgivenforthetransfer;or(3)byoperationoflaw.

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LEGAL MATTERS

CertainlegalmattersinconnectionwiththisofferingwillbepasseduponforusbyRopes&GrayLLP,Boston,Massachusetts.Ropes&GrayLLPandsomeofitsattorneysarelimitedpartnersofRGIP,LP,whichisaninvestorincertaininvestmentfundsadvisedormanagedbyBainCapitalPrivateEquity,LPandoftenaco-investorwithsuchfunds.RGIP,LPindirectlyownslessthan1%ofouroutstandingordinaryshares.ThevalidityoftheissuanceofordinarysharestobesoldinthisofferingwillbepasseduponforusbyLoyens&LoeffLuxembourgS.à.r.l.,Luxembourg.CahillGordon&ReindelLLP,NewYork,NewYorkisactingascounseltotheunderwriter.

EXPERTS

TheauditedfinancialstatementsofTrinseoS.A.incorporatedinthisprospectussupplementbyreferencetotheAnnualReportonForm10-KfortheyearendedDecember31,2015,exceptastheyrelatetoAmericasStyrenicsLLC,andtheeffectivenessofinternalcontroloverfinancialreportingasofDecember31,2015havebeenauditedbyPricewaterhouseCoopersLLP,anindependentregisteredpublicaccountingfirm.Suchfinancialstatements,exceptastheyrelatetoAmericasStyrenicsLLC,andmanagement'sassessmentoftheeffectivenessofinternalcontroloverfinancialreportinghavebeensoincorporatedinrelianceonthereportofsuchindependentregisteredpublicaccountingfirmgivenontheauthorityofsaidfirmasexpertsinauditingandaccounting.

TheconsolidatedfinancialstatementsofAmericasStyrenicsLLC,incorporatedinthisprospectussupplementbyreferencefromTrinseoS.A.'sAnnualReportonForm10-KfortheyearendedDecember31,2015,havebeenauditedbyDeloitte&ToucheLLP,anindependentregisteredpublicaccountingfirm,asstatedintheirreport,whichisincorporatedhereinbyreference.Suchfinancialstatementshavebeensoincorporatedinrelianceuponthereportofsuchfirmgivenupontheirauthorityasexpertsinaccountingandauditing.

WHERE YOU CAN FIND MORE INFORMATION

WehavefiledwiththeSECaregistrationstatementonFormS-3undertheSecuritiesActwithrespectourordinarysharesbeingofferedbythisprospectussupplementandtheaccompanyingprospectus.Thisprospectussupplementandtheaccompanyingprospectusdonotcontainalloftheinformationsetforthintheregistrationstatement.Forfurtherinformationwithrespecttousandtheordinaryshares,referenceismadetotheregistrationstatementanditsexhibits.Statementscontainedinthisprospectussupplementortheaccompanyingprospectusastothecontentsofanycontractorotherdocumentarenotnecessarilycomplete.Wearerequiredtofileannualandquarterlyreports,specialreports,proxystatements,andotherinformationwiththeSEC.Theregistrationstatement,suchreportsandotherinformationcanbeinspectedandcopiedatthePublicReferenceRoomoftheSEClocatedat100FStreet,N.E.,Washington,D.C.20549.Copiesofsuchmaterials,includingcopiesofalloranyportionoftheregistrationstatement,canbeobtainedfromthePublicReferenceRoomoftheSECatprescribedrates.YoucancalltheSECat1-800-SEC-0330toobtaininformationontheoperationofthePublicReferenceRoom.SuchmaterialsmayalsobeaccessedelectronicallybymeansoftheSEC'swebsiteatwww.sec.gov.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

TheSECallowsusto"incorporatebyreference"intothisprospectussupplementandtheaccompanyingprospectusinformationwefilewithit,whichmeansthatwecandiscloseimportantinformationtoyoubyreferringyoutothosedocuments.Theinformationincorporatedbyreferenceisconsideredtobepartofthisprospectussupplementandtheaccompanyingprospectus,andinformationindocumentsthatwefilelaterwiththeSECwillautomaticallyupdateandsupersedeinformationinthisprospectussupplement.Weincorporatebyreferenceintothisprospectussupplementandthe

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accompanyingprospectusthedocumentslistedbelowandanyfuturefilingsmadebyuswiththeSECunderSection13(a),13(c),14or15(d)oftheExchangeAct,except,ineachcase,forinformation"furnished"underItems2.02,7.01or9.01onForm8-Korotherinformation"furnished"totheSECwhichisnotdeemedfiledandnotincorporatedinthisprospectussupplementortheaccompanyingprospectus,untiltheterminationofthisoffering.Weherebyincorporatebyreferencethefollowingdocuments:

• OurannualreportonForm10-KfortheyearendedDecember31,2015,filedwiththeSEConMarch11,2016(FileNo.001-36473),andasamendedonMarch15,2016;

• OurquarterlyreportsonForm10-QforthequartersendedMarch31,2016andJune30,2016,filedwiththeSEConMay5,2016andAugust3,2016,respectively(FileNo.001-36473);

• OurcurrentreportsonForm8-KfiledwiththeSEConJanuary26,2016,February26,2016,March24,2016,April5,2016,May11,2016,May23,2016,June22,2016,July27,2016,August12,2016,August16,2016,August30,2016andAugust31,2016(FileNo.001-36473);and

• ThedescriptionofourordinarysharescontainedintheRegistrationStatementonForm8-A,asfiledwiththeSEConJune2,2014(FileNo.001-36473).

Youmayrequestacopyofthesefilings,atnocost,bywritingortelephoningusatthefollowingaddress:

TrinseoS.A.Attn:CorporateSecretary

1000ChesterbrookBoulevardSuite300

Berwyn,PA19312(610)240-3200

Copiesofthesefilingsarealsoavailable,withoutcharge,ontheSEC'swebsiteatwww.sec.govandonourwebsite,www.trinseo.com,assoonasreasonablypracticableaftertheyarefiledelectronicallywiththeSEC.Theinformationcontainedonourwebsiteisnotapartofthisprospectussupplementortheaccompanyingprospectus.

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Trinseo S.A.37,269,567 Ordinary Shares

Thesellingshareholderidentifiedinthisprospectusmayofferandsellfromtimetotime,inoneormoreseriesorissuancesandontermsthatwillbedeterminedatthetimeoftheoffering,37,269,567ordinarysharesofTrinseoS.A.Wewillnotreceiveanyproceedsfromthesaleofsharesbythesellingshareholder.

Wewillprovidespecifictermsofanyofferinginasupplementtothisprospectus.Anyprospectussupplementmayalsoadd,update,orchangeinformationcontainedinthisprospectus.Youshouldcarefullyreadthisprospectusandtheapplicableprospectussupplementaswellasthedocumentsincorporatedordeemedtobeincorporatedbyreferenceinthisprospectusandtheapplicableprospectussupplementbeforeyoupurchaseanyofthesecuritiesofferedhereby.

OurordinarysharesarelistedontheNewYorkStockExchangeunderthesymbol"TSE."OnMarch14,2016,thelastsalepriceofourordinarysharesasreportedontheNewYorkStockExchangewas$34.67pershare.

Investing in our ordinary shares involves substantial risks. See "Risk Factors" beginning on page 3 of this prospectus toread about factors you should consider before buying our ordinary shares.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed onthe accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

ProspectusdatedMarch15,2016

TABLE OF CONTENTS

Wehavenotauthorizedanyonetoprovideanyinformationortomakeanyrepresentationsotherthanthosecontainedorincorporatedbyreferenceinthisprospectus,anyaccompanyingprospectussupplementorinanyfreewritingprospectuseswehaveprepared.Wetakenoresponsibilityfor,andcanprovidenoassuranceastothereliabilityof,anyotherinformationthatothersmaygiveyou.Thisprospectusandanyaccompanyingprospectussupplementareanoffertosellonlythesharesofferedhereby,butonlyundercircumstancesandinjurisdictionswhereitislawfultodoso.Theinformationcontainedorincorporatedbyreferenceinthisprospectusandanyaccompanyingprospectussupplementiscurrentonlyasofthedateoftheapplicabledocument.

AboutthisProspectus 1AboutTrinseoS.A. 2RiskFactors 3CautionaryNoteRegardingForward-LookingStatements 4UseofProceeds 6SellingShareholder 6PlanofDistribution 7LegalMatters 9Experts 9WhereYouCanFindMoreInformation 9IncorporationofCertainInformationbyReference 9

ABOUT THIS PROSPECTUS

ThisprospectusispartofaregistrationstatementonFormS-3thatwefiledwiththeSecuritiesandExchangeCommission(the"SEC")undertheSecuritiesActof1933,asamended("SecuritiesAct"),usinga"shelf"registrationprocess.Underthisshelfregistrationprocess,thesellingshareholdermay,onacontinuousbasis,inoneormoreofferings,sellorotherwisedisposeofupto37,269,567ordinaryshares.Thisprospectusincorporatesbyreferenceimportantbusinessandfinancialinformationaboutusthatisnotincludedinordeliveredwiththisdocument.Youshouldreadtheadditionalinformationdescribedunder"WhereYouCanFindMoreInformation"and"IncorporationofCertainInformationbyReference."

Wewillnotreceiveanyproceedsfromthesaleorotherdispositionoftheordinarysharesregisteredhereunder.

Wehavenotauthorizedanydealer,agentorotherpersontogiveanyinformationortomakeanyrepresentationotherthanthosecontainedorincorporatedbyreferenceinthisprospectus.Thisprospectusdoesnotconstituteanoffertosellorthesolicitationofanoffertobuyanysecuritiesotherthantheregisteredsecuritiestowhichtheyrelate,nordoesthisprospectusconstituteanoffertosellorthesolicitationofanoffertobuysecuritiesinanyjurisdictiontoanypersontowhomitisunlawfultomakesuchofferorsolicitationinsuchjurisdiction.Youshouldnotassumethattheinformationcontainedinthisprospectusisaccurateonanydatesubsequenttothedatesetforthonthefrontofthedocumentorthatanyinformationwehaveincorporatedbyreferenceiscorrectonanydatesubsequenttothedateofthedocumentincorporatedbyreference,eventhoughthisprospectusandanyaccompanyingprospectussupplementisdeliveredorsecuritiesaresoldonalaterdate.

Unlessotherwiseindicatedorthecontextotherwiserequires,theterms"Trinseo,""we,""us,""our,""ourCompany"and"ourbusiness"refertoTrinseoS.A.togetherwithitsconsolidatedsubsidiaries.Priortoourformation,ourbusinesseswerewholly-ownedbyTheDowChemicalCompany.Werefertoourpredecessorbusinessesas"theStyronbusiness."OnJune17,2010,investmentfundsadvisedormanagedbyBainCapitalPartners,LPacquiredtheStyronbusiness,andDowEuropeHoldingB.V.,whichwerefertoas"DowEurope,"or,togetherwithotheraffiliatesofTheDowChemicalCompany,"Dow,"retainedanownershipinterestintheStyronbusinessthroughanindirectownershipinterestinus.Werefertothistransactionasthe"Acquisition."Referencesto"sellingshareholder"and"Parent"refertoBainCapitalEverestManagerHoldingsSCAdescribedundertheheading"SellingShareholder"onpage6,whomaysellsharesasdescribedinthisprospectus.

Youshouldcarefullyreadtheentireprospectus,includinginformationincorporatedbyreferenceintothisprospectusandthe"RiskFactors"and"CautionaryNoteRegardingForward-LookingStatements"sectionsofthisprospectus,beforedecidingwhethertoinvestinourordinaryshares.

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ABOUT TRINSEO S.A.

Trinseoisaleadingglobalmaterialscompanyengagedinthemanufactureandmarketingofsyntheticrubber,latex,andplastics,includingvariousspecialtyandtechnologicallydifferentiatedproducts.Trinseo'sproductsareincorporatedintoawiderangeofproductsthroughouttheworld,includingtiresandotherproductsforautomotiveapplications,carpetandartificialturfbacking,coatedpaperandpackagingboard,foodpackaging,appliances,medicaldevices,consumerelectronicsandconstructionapplications.Trinseohadapproximately$4.0billioninnetsalesin2015,andasofDecember31,2015had2,270employeesand18manufacturingsitesworldwide.

TrinseoisaLuxembourglimitedliabilitycompany(société anonyme ),witharegisteredofficeat4,rueLouHemmer,L-1748Luxembourg,GrandDuchyofLuxembourgandregisteredwithLuxembourg'sRegisterofCommerceandCompanies(RCS)underRCSnumberB153.549.

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RISK FACTORS

Investing in our ordinary shares involves a high degree of risk. See "Item 1A. Risk Factors" in our most recent Annual Report on Form 10-K incorporated byreference in this prospectus and in any subsequent Quarterly Report on Form 10-Q and the "Risk Factors" section in the applicable prospectus supplement for adiscussion of the factors you should carefully consider before deciding to purchase our ordinary shares.

3

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

Thisprospectus,includinginformationincorporatedbyreferenceherein,containsforward-lookingstatementsincluding,withoutlimitation,statementsconcerningplans,objectives,goals,projections,strategies,futureeventsorperformance,andunderlyingassumptionsandotherstatements,whicharenotstatementsofhistoricalfacts.Forward-lookingstatementsmaybeidentifiedbytheuseofwordslike"expect,""anticipate,""intend,""forecast,""outlook,""will,""may,""might,""potential,""likely,""target,""plan,""contemplate,""seek,""attempt,""should,""could,""would"orexpressionsofsimilarmeaning.Forward-lookingstatementsreflectmanagement'sevaluationofinformationcurrentlyavailableandarebasedonourcurrentexpectationsandassumptionsregardingourbusiness,theeconomyandotherfutureconditions.Becauseforward-lookingstatementsrelatetothefuture,theyaresubjecttoinherentuncertainties,risksandchangesincircumstancesthataredifficulttopredict.Specificfactorsthatmayimpactperformanceorotherpredictionsoffutureactionshave,inmanybutnotallcases,beenidentifiedinconnectionwithspecificforward-lookingstatements.Ouractualresultsmaydiffermateriallyfromthosecontemplatedbytheforward-lookingstatements.Theyareneitherstatementsofhistoricalfactnorguaranteesorassurancesoffutureperformance.Importantfactorsthatcouldcauseactualresultstodiffermateriallyfromthoseintheforward-lookingstatementsincludeeconomic,business,competitive,marketandregulatoryconditionsandthefollowing:

• ourcurrentlevelofindebtedness;

• thestabilityofourjointventures;

• lawsuitsresultingfromproductsoroperations;

• volatilityincostsordisruptioninthesupplyoftherawmaterialsutilizedforourproducts;

• hazardsassociatedwithchemicalmanufacturing;

• thecompetitivenatureofourendmarkets;

• ourcontinuedrelianceonourrelationshipwithTheDowChemicalCompany;

• ourcompliancewithenvironmental,healthandsafetylaws;

• conditionsintheglobaleconomyandcapitalmarkets;

• anydisruptionsinproductionatourmanufacturingfacilities;

• increasesinthecostofenergy;

• ourabilitytomaintainthenecessarylicensesandpermitsweneedforouroperations;

• failuretomaintainaneffectivesystemofinternalcontrols;

• currentinsurancenotcoveringallpotentialexposures;

• changesinlawsandregulationsapplicabletoourbusiness;

• ourdependenceuponkeyexecutivemanagementandanyinabilitytoattractandretainotherqualifiedmanagementpersonnel;

• fluctuationsincurrencyexchangerates;

• strategicacquisitionsaffectingcurrentoperations;

• thelossofcustomers;

• anyinabilitytocontinuetechnologicalinnovationandsuccessfulintroductionofnewproducts;

• anyinabilitytoprotectourtrademarks,patentsorotherintellectualpropertyrights;

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• datasecuritybreaches;

• failureofourassumptionsandprojectionstobeaccurate;

• localbusinessrisksindifferentcountriesinwhichweoperate;

• seasonalityofourbusiness;and

• otherrisksdescribedinthe"RiskFactors"sectionofthisprospectusandtheapplicableprospectussupplement.

Wederivemanyofourforward-lookingstatementsfromouroperatingbudgetsandforecasts,whicharebaseduponmanydetailedassumptions.Whilewebelievethatourassumptionsarereasonable,wecautionthatitisverydifficulttopredicttheimpactofknownfactors,anditisimpossibleforustoanticipateallfactorsthatcouldaffectouractualresults.Importantfactorsthatcouldcauseactualresultstodiffermateriallyfromourexpectations,orcautionarystatements,aredisclosedunderthesectionentitled"RiskFactors"andthesectionsentitled"Management'sDiscussionandAnalysisofFinancialConditionandResultsofOperations"fromourAnnualReportonForm10-KandQuarterlyReportsonForm10-Q,incorporatedbyreferenceintothisprospectus.Allwrittenandoralforward-lookingstatementsattributabletous,orpersonsactingonourbehalf,areexpresslyqualifiedintheirentiretybythecautionarystatementsaswellasothercautionarystatementsthataremadefromtimetotimeinourotherpubliccommunications.Youshouldevaluateallforward-lookingstatementsmadeinthisprospectusandthedocumentsincorporatedbyreferencehereininthecontextoftheserisksanduncertainties.

Wecautionyouthattheimportantfactorsreferencedabovemaynotcontainallofthefactorsthatareimportanttoyou.Inaddition,wecannotassureyouthatwewillrealizetheresultsordevelopmentsweexpectoranticipateor,evenifsubstantiallyrealized,thattheywillresultintheconsequencesoraffectusorouroperationsinthewayweexpect.Theforward-lookingstatementsincludedinthisprospectusandthedocumentsincorporatedbyreferencehereinaremadeonlyasofthedateoftheapplicabledocument.Weundertakenoobligationtopubliclyupdateorreviseanyforward-lookingstatementasaresultofnewinformation,futureeventsorotherwise,exceptasotherwiserequiredbylaw.

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USE OF PROCEEDS

Wewillnotreceiveanyproceedsfromthesaleofourordinarysharesbythesellingshareholder.

SELLING SHAREHOLDER

Thesellingshareholdernamedinthisprospectusmayoffertosellfromtimetotimeupto37,269,567ofourordinaryshares,asprovidedinthisprospectusunderthesectionentitled"PlanofDistribution"andinanyapplicableprospectussupplement.However,wedonotknowwhenorinwhatamountthesellingshareholdermayofferitssharesforsaleunderthisprospectus.ThesellingshareholderreceivedsuchsharesinconnectionwiththeAcquisition.

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Maximum Number of Shares that

may be offered

pursuant to this

Prospectus

Shares owned Prior to the

Offering Shares Owned After the

Offering

Name Number of

Shares Percentage Number of

Shares Percentage BainCapitalEverestManagerHoldingsSCA("Parent")(1) 37,269,567 76.4% 37,269,567

(1) ThegeneralpartnerofourParentisBainCapitalEverestManagerS.à.r.l.("BCEM").Byvirtueoftherelationshipsdescribedinthisfootnote,BCEMmaybedeemedtoexercisevotinganddispositivepowerwithrespecttothesharesheldbyParent.MichelG.Plantevin,AurélienVasseur,ChristopherD.Pappas,StephenThomas,FelixHauser,andStephenM.ZideareeachmanagersofBCEM.ThemanagersofBCEMdisclaimbeneficialownershipofsuchsharestotheextentattributedtothemsolelybyvirtueofservingasamanagerofBCEM.AlloftheoutstandingsharecapitalofBCEMisheldbyBainCapitalEuropeFundIII,L.P.("EuropeFundIII")and,inthatcapacity,EuropeFundIIIhasthepowertoappointthemanagersofBCEM.BainCapitalInvestors,LLC("BCI")isthegeneralpartnerofBainCapitalPartnersEuropeIII,L.P.,whichisthegeneralpartnerofEuropeFundIII.Asaresultoftherelationshipsdescribedabove,BCImaybedeemedtosharebeneficialownershipofthesharesheldbyourParent.Thegovernance,investmentstrategyanddecision-makingprocesswithrespecttoinvestmentsheldbyEuropeFundIIIisdirectedbyBCI'sGlobalPrivateEquityBoard("GPEB"),whichiscomprisedofthefollowingindividuals:StevenBarnes,JoshuaBekenstein,JohnConnaughton,DavidGross-Loh,StephenPagliuca,MichelG.Plantevin,DwightPoler,andJonathanZhu.Byvirtueoftherelationshipsdescribedinthisfootnote,GPEBmaybedeemedtoexercisevotinganddispositivepowerwithrespecttothesharesheldbyourParent.EachofthemembersofGPEBdisclaimsbeneficialownershipofsuchsharestotheextentattributedtosuchmembersolelybyvirtueofservingonGPEB.TheaddressforourParentandBCEMis4,rueLouHemmer,L-1748Luxembourg,GrandDuchyofLuxembourg.EuropeFundIIIhasanaddressofUglandHouse,SouthChurchStreet,GeorgeTown,GrandCayman,KY1-1104CaymanIslandsandBCIhasanaddressc/oBainCapitalPartners,LP,200ClarendonStreet,Boston,Massachusetts02116.TheaddressofMr.Hauserisc/oBainCapitalBeteiligungsberatungGmbHMaximilianstrasse11,80539Munich,Germany.

PLAN OF DISTRIBUTION

Thesellingshareholderwillsellthesecuritiesofferedherebyinoneormoreofthefollowingways(orinanycombinationthere)fromtimetotime:

• toorthroughunderwriters;

• throughagents;

• throughbrokersordealers;

• directlytopurchasers,includingthroughaspecificbidding,auctionorotherprocessorinprivatelynegotiatedtransactions;

• throughacombinationofsuchmethods;or

• throughanyothermethodpermittedbyapplicablelaw.

Aprospectussupplementwilldescribethetermsoftheofferingoftheordinaryshares,includingthefollowing:

• thenameornamesofanyunderwriters,dealersoragentsandtheamountofordinarysharesunderwrittenorpurchasedbyeachofthem;

• thepublicofferingpriceoftheordinaryshares,theproceedstothesellingshareholder,andanydiscounts,commissionsorconcessionsallowedorreallowedorpaidtounderwriters,dealersoragents,andotheritemsconstitutingunderwriters',dealers'oragents'compensation;

• anydelayeddeliveryarrangements;and

• informationaboutthesellingshareholder,includingtherelationshipbetweenthesellingshareholderandus.

Anyofferingpriceandanydiscountsorconcessionsallowedorreallowedorpaidtodealerswillbespecifiedintheprospectussupplementandmaybechangedfromtimetotime.

Onlytheagentsorunderwritersnamedintheprospectussupplementareagentsorunderwritersinconnectionwiththeordinarysharesbeingofferedthereby.

Thesellingshareholdermayauthorizeunderwriters,dealersorotherpersonsactingasouragentstosolicitoffersbycertaininstitutionstopurchasesecuritiesfromthesellingshareholderpursuanttodelayeddeliverycontractsprovidingforpaymentanddeliveryonthedatestatedineachapplicableprospectussupplement.Eachcontractwillbeforanamountnotlessthan,andtheaggregateamountofsecuritiessoldpursuanttosuchcontractsshallnotbelessnormorethan,therespectiveamountsstatedineachapplicableprospectussupplement.Institutionswithwhomthecontracts,whenauthorized,maybemadeincludecommercialandsavingsbanks,insurancecompanies,pensionfunds,investmentcompanies,educationalandcharitableinstitutionsandotherinstitutions,butshallinallcasesbesubjecttoourapproval.Delayeddeliverycontractswillbesubjectonlytothoseconditionssetforthintheprospectussupplement,andtheprospectussupplementwillsetforthanycommissionswepayforsolicitationofthesecontracts.

Agents,underwritersandotherthirdpartiesdescribedabovemaybeentitledtoindemnificationbyusandthesellingshareholderagainstcertaincivilliabilities,includingliabilitiesundertheSecuritiesAct,ortocontributionfromusandthesellingshareholderwithrespecttopaymentswhichtheagents,underwritersorthirdpartiesmayberequiredtomakeinrespectthereof.Agents,underwritersandsuchotherthirdpartiesmaybecustomersof,engageintransactionswith,orperformservicesforusorthesellingshareholderintheordinarycourseofbusiness.Weandthesellingshareholdermayalsouseunderwritersorsuchotherthirdpartieswithwhomweorsuchsellingshareholderhaveamaterial

7

relationship.Weandthesellingshareholderwilldescribethenatureofanysuchrelationshipintheapplicableprospectussupplement.

Certainunderwritersmayusethisprospectusandanyaccompanyingprospectussupplementforoffersandsalesrelatedtomarket-makingtransactionsinourordinaryshares.Theseunderwritersmayactasprincipaloragentinthesetransactions,andthesaleswillbemadeatpricesrelatedtoprevailingmarketpricesatthetimeofsale.Anyunderwritersinvolvedinthesaleofourordinarysharesmayqualifyas"underwriters"withinthemeaningofSection2(a)(11)oftheSecuritiesAct.Inaddition,theunderwriters'commissions,discountsorconcessionsmayqualifyasunderwriters'compensationundertheSecuritiesActandtherulesoftheFinancialIndustryRegulatoryAuthority.

OurordinarysharesarelistedonTheNewYorkStockExchange.Underwritersmaymakeamarketinourordinaryshares,butwillnotbeobligatedtodosoandmaydiscontinueanymarketmakingatanytimewithoutnotice.Wecanmakenoassuranceastothedevelopment,maintenanceorliquidityofanytradingmarketinourordinaryshares.

Certainpersonsparticipatinginanofferingmayengageinoverallotment,stabilizingtransactions,shortcoveringtransactionsandpenaltybidsinaccordancewithrulesandregulationsundertheSecuritiesExchangeActof1934,asamended(the"ExchangeAct").Overallotmentinvolvessalesinexcessoftheofferingsize,whichcreateashortposition.Stabilizingtransactionspermitbidstopurchasetheunderlyingsecuritysolongasthestabilizingbidsdonotexceedaspecifiedmaximum.Shortcoveringtransactionsinvolvepurchasesoftheordinarysharesintheopenmarketafterthedistributioniscompletedtocovershortpositions.Penaltybidspermittheunderwriterstoreclaimasellingconcessionfromadealerwhentheordinarysharesoriginallysoldbythedealerarepurchasedinacoveringtransactiontocovershortpositions.Thoseactivitiesmaycausethepriceoftheordinarysharestobehigherthanitwouldotherwisebe.Ifcommenced,theunderwritersmaydiscontinueanyoftheactivitiesatanytime.

8

LEGAL MATTERS

CertainlegalmattersinconnectionwiththisofferingwillbepasseduponforusbyRopes&GrayLLP,Boston,Massachusetts.Ropes&GrayLLPandsomeofitsattorneysarelimitedpartnersofRGIP,LP,whichisaninvestorincertaininvestmentfundsadvisedormanagedbyBainCapitalPartners,LPandoftenaco-investorwithsuchfunds.RGIP,LPindirectlyownslessthan1%ofouroutstandingordinaryshares.ThevalidityoftheissuanceofordinarysharestobesoldinthisofferingwillbepasseduponforusbyLoyens&LoeffLuxembourgS.à.r.l.,Luxembourg.

EXPERTS

TheauditedfinancialstatementsofTrinseoS.A.incorporatedinthisProspectusbyreferencetotheAnnualReportonForm10-KfortheyearendedDecember31,2015,exceptastheyrelatetoAmericasStyrenicsLLC,andtheeffectivenessofinternalcontroloverfinancialreportingasofDecember31,2015havebeenauditedbyPricewaterhouseCoopersLLP,anindependentregisteredpublicaccountingfirm.Suchfinancialstatements,exceptastheyrelatetoAmericasStyrenicsLLC,andmanagement'sassessmentoftheeffectivenessofinternalcontroloverfinancialreportinghavebeensoincorporatedinrelianceonthereportofsuchindependentregisteredpublicaccountingfirmgivenontheauthorityofsaidfirmasexpertsinauditingandaccounting.

TheconsolidatedfinancialstatementsofAmericasStyrenicsLLC,incorporatedinthisprospectusbyreferencefromTrinseoS.A.'sAnnualReportonForm10-KfortheyearendedDecember31,2015,havebeenauditedbyDeloitte&ToucheLLP,anindependentregisteredpublicaccountingfirm,asstatedintheirreport,whichisincorporatedhereinbyreference.Suchfinancialstatementshavebeensoincorporatedinrelianceuponthereportofsuchfirmgivenupontheirauthorityasexpertsinaccountingandauditing.

WHERE YOU CAN FIND MORE INFORMATION

WehavefiledwiththeSECaregistrationstatementonFormS-3undertheSecuritiesActwithrespecttoourordinarysharesbeingofferedbythisprospectus.Thisprospectus,whichformsapartoftheregistrationstatement,doesnotcontainalloftheinformationsetforthintheregistrationstatement.Forfurtherinformationwithrespecttousandtheordinaryshares,referenceismadetotheregistrationstatementandtheexhibitsandschedulesfiledasapartthereof.Statementscontainedinthisprospectusastothecontentsofanycontractorotherdocumentarenotnecessarilycomplete.WearesubjecttotheinformationalrequirementsoftheSecuritiesExchangeActof1934and,inaccordancetherewith,wefilereportsandotherinformationwiththeSEC.Theregistrationstatement,suchreportsandotherinformationcanbeinspectedandcopiedatthePublicReferenceRoomoftheSEClocatedat100FStreet,N.E.,Washington,D.C.20549.Copiesofsuchmaterials,includingcopiesofalloranyportionoftheregistrationstatement,canbeobtainedfromthePublicReferenceRoomoftheSECatprescribedrates.YoucancalltheSECat1-800-SEC-0330toobtaininformationontheoperationofthePublicReferenceRoom.ThesematerialsmayalsobeaccessedelectronicallyfromtheSEC'swebsite,www.sec.gov.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

TheSECallowsusto"incorporatebyreference"intothisprospectusinformationwefilewithit,whichmeansthatwecandiscloseimportantinformationtoyoubyreferringtothesedocuments.TheinformationincorporatedbyreferenceisconsideredtobepartofthisprospectusandinformationindocumentsthatwefilelaterwiththeSECwillautomaticallyupdateandsupersedeinformationinthisprospectus.WeincorporatebyreferenceintothisprospectusthedocumentslistedbelowandanyfuturefilingsmadebyuswiththeSECunderSection13(a),13(c),14,or15(d)oftheExchangeAct,exceptforinformationfurnishedunderItems2.02,7.01,or9.01onForm8-Korotherinformation"furnished"

9

totheSECwhichisnotdeemedfiledandnotincorporatedinthisprospectus,untiltheterminationoftheofferingofsecuritiesdescribedintheapplicableprospectussupplement.Weherebyincorporatebyreferencethefollowingdocuments:

• OurannualreportonForm10-KfortheyearendedDecember31,2015,filedwiththeSEConMarch11,2016(FileNo.001-36473),andasamendedonMarch15,2016;

• OurcurrentreportsonForm8-KfiledwiththeSEConJanuary26,2016andFebruary26,2016;and

• ThedescriptionofourordinarysharescontainedintheRegistrationStatementonForm8-A,asfiledwiththeSEConJune2,2014(FileNo.001-36473).

Youmayrequestacopyofthesefiling,atnocost,bywritingortelephoningusat:

TrinseoS.A.Attn:CorporateSecretary

1000ChesterbrookBoulevardSuite300

Berwyn,PA19312(610)240-3200

Copiesofthefilingsarealsoavailable,withoutchargeontheSEC'swebsite,www.sec.gov,andonourwebsite,www.trinseo.com,assoonasreasonablypracticableaftertheyarefiledelectronicallywiththeSEC.Theinformationcontainedonourwebsiteisnotapartofthisprospectus.

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TableofContents

Trinseo S.A.10,669,567 Ordinary Shares

PROSPECTUS SUPPLEMENT

Morgan Stanley