X0306 4 2020-03-09 0 0001519061 Trinseo S.A. TSE 0001660737 BOZICH FRANK A 1000 CHESTERBROOK BLVD. SUITE 300 BERWYN PA 19312 1 1 0 0 President and CEO Ordinary Shares 2020-03-09 4 P 0 12000 16.70 A 96770 D Price reflects the weighted average purchase price for the purchase transactions made on the date reported above. Purchase prices ranged from $16.56 to $16.85. The reporting person will provide, upon request by the Staff, Trinseo S.A., or any security holder of Trinseo S.A., full information regarding the number of shares purchased or sold at each respective price within the range presented in this footnote. /s/ Angelo Chaclas, attorney-in-fact 2020-03-10