FINANCIAL INSTITUTIONS INC

Expectations for our directors, officers and employees are memorialized in our Code of Business Conduct and Ethics Policy (“Code of Ethics”) that is annually reviewed and approved by our Board of Directors. The Code of Ethics is applicable to all employees and covers professional conduct, including, but not limited to, conflicts of interest, safeguarding of confidential information, protecting company assets, anti-trust compliance, fair and responsible banking, and financial responsibility. New and existing employees and directors (on an annual basis) are required to acknowledge receipt of and compliance with the Code of Ethics.

6 Financial Institutions, Inc.

Additionally, we have a code of ethics for the CEO, CFO and senior financial officers that sets additional and heightened expectations for honest and ethical conduct and compliance with applicable laws, rules and regulations applicable to financial related matters (this code of ethics and the Code of Ethics collectively are referred to as “Ethics Codes”). Each applicable employee and director must annually review and affirm their intent to comply with the Ethics Codes.

Current versions of these codes may be viewed on our website atwww.FISI-Investors.com by clicking on “Governance,” then on “Governance Documents.” Exceptions or amendments to any provision of the Ethics Codes must be approved by the Chief Compliance Officer (“CCO”) and reported to and ratified or approved by the Board. We intend to notify shareholders of any exceptions or amendments granted on our website atwww.FISI-Investors.com. We did not grant any exceptions or approve any amendments during 2025 and our investor website includes the current versions of the Ethics Codes.

CERTAIN RELATIONSHIPS AND RELATED PARTY TRANSACTIONS

Our Related Party Transactions Policy is similarly reviewed and updated annually and provides for the handling and oversight of related party transactions, as defined under Item 404(a) of SEC Regulation S-K. Our CCO is notified when a potential related party transaction is being contemplated. Potential transactions are referred to the Board’s Audit Committee to determine whether the transaction is a related party transaction. If the Audit Committee determines that the potential transaction is a related party transaction, the Committee decides whether to approve or decline the proposed transaction. In determining whether to approve a potential related party transaction, the Audit Committee considers regulatory requirements, whether the transaction is consistent with the Ethics Codes, and all other factors it deems appropriate using its business judgment.

During 2025, certain of our directors and executive officers and their respective affiliates were customers of and had loans and/or other transactions with us. Except as set forth below, loans and other transactions were made in the ordinary course of business on substantially the same terms, including interest rates and collateral, as those prevailing at the time they were made for comparable loans and other transactions with persons not related to us. These loans and other transactions did not involve more than the normal risk of collectability or present other unfavorable features to the Company. Presently, we have such loans and expect to have similar loans with our directors, executive officers, 5% or greater shareholders and their affiliates in the future.

All loans to the Bank’s directors and executive officers are made in conformity with the Federal Reserve Act and applicable regulations. The Bank provides certain banking benefits to its employees, including its executive officers, through an employee banking program. Pursuant to that program, employees are entitled to modest interest rate discounts on certain residential real estate and consumer loans. Federal regulations permit executive officers to receive the same terms that are widely available to other employees as long as the executive officers are not given preferential treatment compared to other participating employees.

The following table sets forth loans made by the Bank to its executive officers where the largest amount of all indebtedness outstanding during the year ended December 31, 2025 exceeded $120,000, and where the borrowers received reduced interest rates pursuant to the employee banking program described above.

2026 Proxy Statement 7