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Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended : December 31 , 2020 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from Trinseo S.A. ( Exact name of registrant as specified in its charter ) Luxembourg ( State or other jurisdiction of incorporation or organization ) to Commission File Number : 001-36473 1000 Chesterbrook Boulevard , Suite 300 Berwyn , PA 19312 ( Address of Principal Executive Offices ) Title of Each Class Ordinary Shares , par value $ 0.01 per share ( 610 ) 240-3200 ( Registrant's telephone number ) N / A ( I.R.S. Employer Identification Number ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol TSE Name of Each Exchange on Which Registered New York Stock Exchange Securities registered pursuant to Section 12 ( g ) of the Act : None No No 区 Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes No Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No □ Accelerated filer Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company , or an emerging growth company . See the definitions of " large accelerated filer , " " accelerated filer , " " smaller reporting company , " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer Non - accelerated filer Smaller reporting company Emerging growth company If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . Indicate by check mark whether the Company is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes As of February 16 , 2021 , there were 38,440,043 shares of the registrant's ordinary shares outstanding . The aggregate market value of the voting and non - voting shares of the registrant held by non - affiliates of Trinseo S.A. computed by reference to the closing price of the registrant's common shares on the New York Stock Exchange as of June 30 , 2020 was approximately $ 833,032,870 . No " Documents Incorporated by Reference Portions of the registrant's definitive proxy statement for the 2020 annual general meeting of shareholders to be filed with the Securities and Exchange Commission pursuant to Regulation 14A of the Securities Exchange Act of 1934 are incorporated by reference into Part III of this report .