X0508 4 2025-03-18 0000723188 COMMUNITY FINANCIAL SYSTEM, INC. CBU 0001486056 Bolus Mark J. C/O COMMUNITY FINANCIAL SYSTEM, INC. 5790 WIDEWATERS PARKWAY DEWITT NY 13214 1 0 Common Stock 2025-03-19 4 M 0 1430 0 A 103815.699 D Common Stock 5750.455 I By Austin Bolus Trust Common Stock 7872.984 I By Mark Bolus Trust Common Stock 5750.455 I By Noah Bolus Trust Common Stock 5750.455 I By Paige Bolus Trust Common Stock 5750.455 I By Taylor Bolus Trust Phantom Stock (Deferred Stock Units) 2025-03-18 4 A 0 1225 0 A Common Stock 1225 3897.7862 D Phantom Stock (Deferred Stock Units) 2025-03-19 4 M 0 1430 0 D Common Stock 1430 2467.413 D On March 19, 2025, the reporting person's phantom stock units were settled for 1,430 shares of Community Financial System, Inc. common stock, and .3732 shares were settled in cash at the price of $58.10 per share. Includes 616.63 shares acquired on January 10, 2025 pursuant to the Community Financial System, Inc. Dividend Reinvestment Plan. Includes 44.508 shares acquired on January 10, 2025 pursuant to the Community Financial System, Inc. Dividend Reinvestment Plan. Includes 60.946 shares acquired on January 10, 2025 pursuant to the Community Financial System, Inc. Dividend Reinvestment Plan. The reporting person has received deferred stock units under the Community Financial System, Inc. 2022 Long-Term Incentive Plan, as amended (the "Plan"). Each phantom stock unit which represents a deferred stock unit is the economic equivalent of one share of Community Financial System, Inc. common stock and will be settled in common stock at a predetermined date. /s/ Danielle M. Cima, pursuant to a Confirming Statement executed by Mark J. Bolus 2025-03-20