COMMUNITY BANK SYSTEM, INC.

Q: Jun 30 2026

Q: Mar 31 2026

FY: Dec 31 2025

Q: Sep 30 2025

Q: Jun 30 2025

Q: Mar 31 2025

FY: Dec 31 2024

Q: Sep 30 2024

Q: Jun 30 2024

Q: Mar 31 2024

FY: Dec 31 2023

Q: Sep 30 2023

Q: Jun 30 2023

Q: Mar 31 2023

FY: Dec 31 2022

Q: Sep 30 2022

Q: Jun 30 2022

Q: Mar 31 2022

FY: Dec 31 2021

Q: Sep 30 2021

Regulation FD Disclosure

Results of Operations and Financial Condition

Other Events

Submission of Matters to a Vote of Security Holders

Regulation FD Disclosure

Results of Operations and Financial Condition

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

Regulation FD Disclosure

Results of Operations and Financial Condition

Regulation FD Disclosure

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

Regulation FD Disclosure

Other Events

Results of Operations and Financial Condition

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

Other Events

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

Results of Operations and Financial Condition

Other Events

Submission of Matters to a Vote of Security Holders

Registration statement under Securities Act of 1933 to be offered to employees pursuant to certain plans

Registration statement under Securities Act of 1933 to be offered to employees pursuant to certain plans

Registration statement under Securities Act of 1933 to be offered to employees pursuant to certain plans

Post Effective Amendment to S-8

Registration statement under Securities Act of 1933 to be offered to employees pursuant to certain plans

Written communication about a business combination transaction (Rule 425)

Written communication about a business combination transaction (Rule 425)

Written communication about a business combination transaction (Rule 425)

Written communication about a business combination transaction (Rule 425)

Written communication about a business combination transaction (Rule 425)

Written communication about a business combination transaction (Rule 425)

Written communication about a business combination transaction (Rule 425)

Prospectus Supplement for Primary Offering

Notice of Effectiveness

Registration statement under Securities Act of 1933 (amendment)

Registration statement under Securities Act of 1933

Written communication about a business combination transaction (Rule 425)

Written communication about a business combination transaction (Rule 425)

Registration statement under Securities Act of 1933 to be offered to employees pursuant to certain plans

Registration statement under Securities Act of 1933 to be offered to employees pursuant to certain plans

Additional Information for Proxy Statement/ Votes

Definitive Proxy Statement

Definitive Proxy Statement

Additional Information for Proxy Statement/ Votes

Definitive Proxy Statement

Additional Information for Proxy Statement/ Votes

Definitive Proxy Statement

Additional Information for Proxy Statement/ Votes

Additional Information for Proxy Statement/ Votes

Definitive Proxy Statement

Additional Information for Proxy Statement/ Votes

Additional Information for Proxy Statement/ Votes

Definitive Proxy Statement

Additional Information for Proxy Statement/ Votes

Definitive Proxy Statement

Additional Information for Proxy Statement/ Votes

Preliminary Proxy Statement

Definitive Proxy Statement

Additional Information for Proxy Statement/ Votes

Definitive Proxy Statement

Vaccaro John A

Sullivan Michele

Singh Savneet

Vaccaro John A

Hall Brenda M

FMR LLC

STEELE SALLY A

Bolus Mark J.

Bolus Mark J.

Sullivan Michele

Vaccaro John A

Durkee Deresa Fischer

STICKELS ERIC

STICKELS ERIC

STICKELS ERIC

FMR LLC

Wlos Marya Burgio

Parente John

Knauss Jeffery J

Pecor Raymond C III

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual Report Scanned (Paper)

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual Report Scanned (Paper)

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual Report Scanned (Paper)

Letter from the SEC

Correspondence with the SEC

Letter from the SEC

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Correspondence with the SEC

Letter from the SEC

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Annual reports of employee stock purchase savings and similar plans pursuant to Section 15(d)

Letter from the SEC

Correspondence with the SEC

Letter from the SEC