Form 4 for CBU COMMUNITY FINANCIAL SYSTEM, INC.

Accepted 2026-03-17 00:00:00 ET · period of report 2026-03-16 · accession 0000723188-26-000045 · SEC index · Original document

Summary rows

Aggregated the way they appear in lists: one row per insider, transaction code and security table.

X	Filed	Traded	Ticker	Insider	Title	Type	Price	Qty	Owned	ΔOwn	Value
D	2026-03-17	2026-03-16	CBU	STICKELS ERIC	Dir	M - OptEx	—	+250	33.6K	+0.7%	—
D	2026-03-17	2026-03-16	CBU	STICKELS ERIC	Dir	M - OptEx	—	-250	4,015	-6%	—

Purchase Sale Sale after option exercise All abbreviations

#	Table	Security	Date	Code	A/D	Shares	Price	Owned after	Own	Exercise / expiry	Underlying	Footnotes
1	Common	Common Stock	2026-03-16	M	A	250	—	33,592	D	—	—	(F1) 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."
2	Derivative	Phantom Stock (Deferred Stock Units)	2026-03-16	M	D	250	—	4,014.54	D	— · — to —	250 Common Stock	(F1) 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." (F3) 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. (F2) 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.