X0508 4 2026-03-16 0000723188 COMMUNITY FINANCIAL SYSTEM, INC. CBU 0001201821 STICKELS ERIC C/O COMMUNITY FINANCIAL SYSTEM, INC. 333 BUTTERNUT DRIVE SYRACUSE NY 13214 1 0 Common Stock 2026-03-16 4 M 0 250 A 33592 D Phantom Stock (Deferred Stock Units) 2026-03-16 4 M 0 250 D Common Stock 250 4014.5421 D On March 16, 2026, the reporting person's phantom stock units were settled for 250 shares of Community Financial System, Inc. common stock, and .9119 shares were settled in cash at the price of $57.42 per share." The reporting person has received deferred stock units under the Community Financial System, Inc. 2022 Long-Term Incentive Plan, as amended (the "LTIP"). 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. Includes 32.1998, 35.6078 and 32.6668 units of phantom stock acquired on July 10, 2025, October 10, 2025 and January 12, 2026 under the Plan's dividend reinvestment feature. Danielle M. Cima, pursuant to a Confirming Statement executed by Eric E. Stickels 2026-03-17