X0206 3 2020-05-01 0 0001519061 Trinseo S.A. TSE 0001811002 Reverberi Francesca C/O TRINSEO S.A. 1000 CHESTERBROOK BLVD., SUITE 300 BERWYN PA 19312 0 1 0 0 VP, Eng Mtrls & Synth Rubber Ordinary Shares 1184 D Ordinary Shares 1807 D Ordinary Shares 5044 D Ordinary Shares 2250 D Option to Purchase Ordinary Shares 26.97 2025-02-22 Ordinary Shares 1173 D Option to Purchase Ordinary Shares 71.45 2026-02-16 Ordinary Shares 1668 D Option to Purchase Ordinary Shares 81.20 2027-02-22 Ordinary Shares 1845 D Option to Purchase Ordinary Shares 51.02 2028-02-26 Ordinary Shares 2564 D Option to Purchase Ordinary Shares 24.30 2029-02-25 Ordinary Shares 8007 D Represents ordinary shares issuable pursuant to a restricted stock unit award granted on 2/22/2018, which will vest in full on the third anniversary of the grant date. Represents ordinary shares issuable pursuant to a restricted stock unit award granted on 2/26/2019, which will vest in full on the third anniversary of the grant date. Represents ordinary shares issuable pursuant to a restricted stock unit granted on 2/25/2020, which will vest in full on the third anniversary of the grant date. Represents options that were granted on 2/22/2016, which vested in three equal annual installments beginning on the first anniversary of the grant date. Represents options that were granted on 2/16/2017, which vested in three equal annual installments beginning on the first anniversary of the grant date. Represents options that were granted on 2/22/2018, which vest in three equal annual installments beginning on the first anniversary of the grant date. Represents options that were granted on 2/26/2019, which vest in three equal annual installments beginning on the first anniversary of the grant date. Represents options that were granted on 2/25/2020, which vest in three equal annual installments beginning on the first anniversary of the grant date. Represents ordinary shares directly held. /s/ Erik Johnson, attorney-in-fact 2020-05-08