Forward Looking Statement

This presentation contains comments or information that constitute forward-looking statements (within the meaning of the Private Securities Litigation Reform Act of 1995), which involve significant risks and uncertainties. Forward-looking statements often use words such as “anticipate,” “could,” “target,” “expect,” “estimate,” “intend,” “plan,” “goal,” “forecast,” “believe,” or other words of similar meaning. These statements are based on the current beliefs and expectations of Community Financial System, Inc.’s (the “Company” or “CFSI”) management and are subject to significant risks and uncertainties. Actual results may differ materially from the results discussed in the forward-looking statements. Moreover, the Company’s plans, objectives and intentions are subject to change based on various factors (some of which are beyond the Company’s control). Factors that could cause actual results to differ from those discussed in the forward-looking statements include: (1) adverse developments in the banking industry related to recent bank failures and the potential impact of such developments on customer confidence and regulatory responses to these developments; (2) current and future economic and market conditions, including the effects of changes in housing or vehicle prices, higher unemployment rates, disruptions in the commercial real estate market, labor shortages, supply chain disruption, inability to obtain raw materials and supplies, U.S. fiscal debt, budget and tax matters, geopolitical matters and conflicts, and any changes in global economic growth; (3) the effect of, and changes in, monetary and fiscal policies and laws, including future changes in Federal and state statutory income tax rates and interest rate and other policy actions of the Board of Governors of the Federal Reserve System; (4) the effect of changes in the level of checking or savings account deposits on the Company’s funding costs and net interest margin including the possibility of a sudden withdrawal of the Company’s deposits due to rapid spread of information or disinformation regarding the Company’s well-being; (5) future provisions for credit losses on loans and debt securities; (6) changes in nonperforming assets; (7) the effect of a fall in stock market or bond prices on the Company’s fee income businesses, including its employee benefit services, wealth management, and insurance businesses; (8) risks related to credit quality; (9) inflation, interest rate, liquidity, market and monetary fluctuations; (10) the strength of the U.S. economy in general and the strength of the local economies where the Company conducts its business; (11) the timely development of new products and services and customer perception of the overall value thereof (including features, pricing and quality) compared to competing products and services; (12) changes in consumer spending, borrowing and savings habits; (13) technological changes and implementation and financial risks associated with transitioning to new technology-based systems involving large multi-year contracts; (14) the ability of the Company to maintain the security, including cybersecurity, of its financial, accounting, technology, data processing and other operating systems, facilities and data, including customer data; (15) effectiveness of the Company’s risk management processes and procedures, reliance on models which may be inaccurate or misinterpreted, the Company’s ability to manage its credit or interest rate risk, the sufficiency of its allowance for credit losses and the accuracy of the assumptions or estimates used in preparing the Company’s financial statements and disclosures; (16) failure of third parties to provide various services that are important to the Company’s operations; (17) any acquisitions or mergers that might be considered or consummated by the Company and the costs and factors associated therewith, including differences in the actual financial results of the acquisition or merger compared to expectations and the realization of anticipated cost savings and revenue enhancements; (18) the ability to maintain and increase market share and control expenses; (19) the nature, timing and effect of changes in banking regulations or other regulatory or legislative requirements affecting the respective businesses of the Company and its subsidiaries, including changes in laws and regulations concerning taxes, accounting, banking, service fees, risk management, securities, capital requirements and other aspects of the financial services industry; (20) changes in the Company’s organization, compensation and benefit plans and in the availability of, and compensation levels for, employees in its geographic markets; (21) the outcome of pending or future litigation and government proceedings; (22) the effect of opening new branches to expand the Company’s geographic footprint, including the cost associated with opening and operating the branches and the uncertainty surrounding their success including the ability to meet expectations for future deposit and loan levels and commensurate revenues; (23) the effects of natural disasters could create economic and financial disruption; (24) other risk factors outlined in the Company’s filings with the SEC from time to time; and (25) the success of the Company at managing the risks of the foregoing. The foregoing list of important factors is not all-inclusive. For more information about factors that could cause actual results to differ materially from the Company’s expectations, refer to the discussion under the heading “Item 1A. Risk Factors” in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2023 as filed with the SEC on February 29, 2024. Any forward-looking statements speak only as of the date on which they are made and the Company does not undertake any obligation to update any forward-looking statement, whether written or oral, to reflect events or circumstances after the date on which such statement is made. If the Company does update or correct one or more forward-looking statements, investors and others should not conclude that the Company will make additional updates or corrections with respect thereto or with respect to other forward-looking statements.

Note Regarding Non‐GAAP Financial Measures

**The Company also provides supplemental reporting of its results on an “operating”, “core”, or “tangible” basis. During the first quarter of 2024, the Company modified the presentation of its non-GAAP operating results to exclude amortization of intangible assets which the Company believes better reflects core performance across its segments and enhances comparability to both banking and nonbanking organizations. The prior period has been recast to conform to the current period presentation. Results on an “operating” basis exclude the after-tax effects of acquisition expenses, litigation accrual, restructuring expenses, gain on debt extinguishment, gain (loss) on sales of investment securities, unrealized gain (loss) on equity securities and amortization of intangible assets. Results on a “tangible” basis exclude goodwill and intangible asset balances, net of accumulated amortization and applicable deferred tax amounts. Although these items are non-GAAP measures, the Company’s management believes this information helps investors and analysts measure underlying core performance and improves comparability to other organizations that have not engaged in acquisitions or restructuring activities. In addition, the Company provides supplemental reporting for “operating pre-tax, pre-provision net revenues,” which excludes the provision for credit losses, acquisition expenses, litigation accrual, restructuring expenses, gain on debt extinguishment, gain (loss) on sales of investment securities, unrealized gain (loss) on equity securities and amortization of intangible assets from income before income taxes. Results on a core income basis are defined as net income after taxes and before extraordinary items, less net income attributable to noncontrolling interest, gain or loss on the sale of securities, amortization of intangibles, goodwill and nonrecurring items. Although operating pre-tax, pre-provision net revenue is a non-GAAP measure, the Company’s management believes this information helps investors and analysts measure and compare the Company’s performance through a credit cycle by excluding the volatility in the provision for credit losses associated with the impact of CECL, helps investors and analysts measure underlying core performance and improves comparability to other organizations that have not engaged in acquisitions or restructuring activities. The Company also provides supplemental reporting of its interest income, net interest income and net interest margin on a fully tax-equivalent (“FTE”) basis, which includes an adjustment to interest income and net interest income that represents taxes that would have been paid had nontaxable investment securities and loans been taxable. Although fully tax-equivalent interest income, net interest income and net interest margin are non-GAAP measures, the Company’s management believes this information helps enhance comparability of the performance of assets that have different tax liabilities. This presentation includes a reconciliation of each non-GAAP financial measure to the most comparable GAAP equivalent. The disclosures within this presentation are unaudited.