X0508 4 2025-03-07 0000723188 COMMUNITY FINANCIAL SYSTEM, INC. CBU 0001866135 Karaivanov Dimitar C/O COMMUNITY FINANCIAL SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 1 President & CEO 0 Common Stock 2025-03-07 4 A 0 3391.9843 0 A 21063.9843 D Common Stock 2660.7151 I By 401(k) Plan On March 7, 2025, the Compensation Committee approved the vesting of the three-year performance-based restricted stock award, granted to the reporting person in 2022, based on achievement of predetermined performance criteria at the target level. The reporting person received 3,069 shares of common stock under the award and 322.9843 shares of common stock acquired under the dividend reinvestment feature of the Community Financial System, Inc. 2022 Long-Term Incentive Plan, as amended (the "Plan"). The number of shares reported herein acquired pursuant to Community Financial System, Inc.'s 401(k) Plan and are based on a current plan statement. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Dimitar Karaivanov 2025-03-11