2024 ANNUAL REPORT 2 | NBT BANCORP INC. Company Profile • NBT Bancorp Inc. is a financial holding company incorporated in 1986 in the state of Delaware. • The Company primarily operates through NBT Bank, N.A. and two financial services companies. • NBT Bank, N.A. offers personal banking, commercial banking and wealth management services through digital channels and 157 banking locations in New York, Pennsylvania, Vermont, Massachusetts, New Hampshire, Maine and Connecticut. The merger of Evans Bank into NBT Bank planned for May 2025 will add 18 new locations in the Buffalo and Rochester markets. • EPIC Retirement Plan Services is a national benefits administration firm based in Rochester, NY with locations in St. Louis, MO, Peoria, IL and Portland, ME. The Company’s retirement plan services business also includes The TPA Experts with locations in New Gloucester, ME, Bedford, NH and West Des Moines, IA. • NBT Insurance Agency is a full-service insurance agency based in Norwich, NY. FOR THE YEAR 2024 2023 PERFORMANCE Net income. . . . . . . . . . . . . . . . . . . . . . . . . . . . $140,641 $118,782 Return on average assets. . . . . . . . . . . . . . . 1.04% 0.95% Return on average tangible equity. . . . . . 13.75% 13.02% Net interest margin. . . . . . . . . . . . . . . . . . . . . 3.23% 3.29% PER COMMON SHARE DATA Diluted earnings. . . . . . . . . . . . . . . . . . . . . . . . $2.97 $2.65 Cash dividends. . . . . . . . . . . . . . . . . . . . . . . . . $1.32 $1.24 Dividend yield. . . . . . . . . . . . . . . . . . . . . . . . . . 2.76% 2.96% Tangible book value per share. . . . . . . . . . $23.88 $21.72 AT DECEMBER 31 BALANCE SHEET DATA Total assets. . . . . . . . . . . . . . . . . . . . . . . . . . . . $13,786,666 $13,309,040 Total loans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . $9,969,910 $9,650,713 Allowance for loan losses. . . . . . . . . . . . . . . $116,000 $114,400 Deposits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $11,546,761 $10,968,994 Total shareholders’ equity. . . . . . . . . . . . . . . $1,526,141 $1,425,691 ASSET QUALITY Net charge-offs to average loans. . . . . . . . 0.18% 0.19% Nonperforming loans to total loans. . . . . . 0.52% 0.39% Nonperforming assets to total assets. . . . 0.38% 0.28% Allowance for loan losses to total loans. . 1.16% 1.19% CAPITAL Common equity tier 1 capital ratio. . . . . . . 11.93% 11.57% Tier 1 capital ratio. . . . . . . . . . . . . . . . . . . . . . . 12.83% 12.50% Total risk-based capital ratio. . . . . . . . . . . . 15.03% 14.75% Closing stock price. . . . . . . . . . . . . . . . . . . . . $47.76 $41.91 Market capitalization. . . . . . . . . . . . . . . . . . . $2,254,010 $1,974,376 Financial Highlights (In thousands, except per share data) 87TH TOTAL ASSETS $13.79B TOTAL DEPOSITS $11.55B NONINTEREST INCOME TO REVENUE* 30% *Excludes gains/losses on sale of securities LARGEST U.S. BANK HOLDING COMPANY $9.97B TOTAL LOANS 3 Fellow Shareholders, Our operating performance in 2024 reflects NBT’s core strengths: • We continue to be a high-performing community bank with a strong capital position and a traditional bank business model built on highly diversified loan and deposit portfolios. • We have a consistent track record of organic growth, selectively balanced with market and product expanding acquisitions. • Our fee-based businesses, including wealth management, retirement plan services and insurance, provide us with diversified income sources. We reported earnings per diluted share of $2.97 and net income of $140.6 million for the full year 2024. Net interest income for the year increased by 5.8% from 2023. Three consecutive quarters of growth in net interest income and margin, generated by our talented bankers along with strong performances by the professionals in each of our fee-based businesses, were the key drivers behind these positive results. We achieved loan growth of 3.3%, or 5.6% excluding consumer portfolios in a planned runoff status. Our total loan portfolio increased to $9.97 billion at year-end with a balanced mix of 53% commercial loans and 47% consumer loans. Total deposits increased 5.3% in 2024 to $11.55 billion at year-end. We maintained our diverse and granular deposit mix with over 561,000 accounts and an average balance per account of $20,574. Our deposit portfolio consists of 58% no and low-cost checking and savings accounts and 42% in generally higher yielding time and money market accounts. While the interest rate environment in 2024 was not marked by the significant volatility of 2023, net interest income generation was still challenged by an inverted yield curve. This brought further emphasis to the advantage of diversification that our fee-based businesses provide. Non- interest income made up 30% of our total revenue for the year, excluding net securities gains and losses. Revenues for EPIC Retirement Plan Services, NBT Insurance Agency and the Wealth Management division of NBT Bank were up 18% over the prior year. Together, these businesses have achieved a five-year combined annual growth rate of 9% supported by successful organic growth strategies and the opportunistic acquisition of smaller, like-minded firms to add to our scale. To Our Shareholders 2024 ANNUAL REPORT | Non-Owner Occupied Commercial Real Estate 31% Owner Occupied Commercial Real Estate 8% Residential Real Estate 22% Commercial & Industrial 14% Other Consumer 1% Indirect Auto 13% Residential Solar 8% Home Equity 3% $9.97B Total Loans Time 12% Demand (Noninterest Bearing) 30% Money Market 30% Savings and NOW 28% $11.55B Total Deposits Retirement Plan Administration 32% Wealth Management 24% Card Services 13% Insurance Services 10% Other Banking Services 16% Bank Owned Life Insurance 5% 2024 Fee Income Composition 4 | NBT BANCORP INC. Leadership Transition. As our team focused on delivering best-in-class service to our customers and executing our long- term growth strategies in 2024, we carried out the succession plan we announced at the outset of the year. Scott Kingsley stepped into the role of President and Chief Executive Officer of the Company in May following the retirement of John Watt, who remains on the Board of Directors as Vice Chairman. Also in May, Joe Stagliano was appointed President of NBT Bank. Annette Burns was promoted to Chief Financial Officer, and Shauna Hyle was elevated to Executive Vice President, Retail Community Banking. This transition presented members of our Executive Management Team with new opportunities to apply their talents and substantial experience, and it also created advancement opportunities for others within the organization that demonstrates the strength of our leadership development initiatives and programs. The commitment and alignment of the entire Executive Management Team and the support of the Board of Directors— and particularly John Watt—resulted in a smooth and successful transition. Growth Opportunities. At NBT, we have experienced productive growth over the decades, including our expansion into New England that started 15 years ago when we opened our first location in Burlington, Vermont. The growth of our footprint to seven northeastern states has provided NBT with opportunities to deploy our strong liquidity and capital positions into new and contiguous markets. We merged Salisbury Bank into NBT Bank in August 2023. In 2024, we benefited from the full-year impact of this partnership with our fully integrated team members in northwest Connecticut, the Berkshires and the Hudson Valley making strong contributions to our success. Now, we are poised to expand our footprint in a new direction— the Western Region of New York—as we build out our franchise west of Interstate 81 through what we are confident will be an impactful acquisition. In September 2024, NBT and Evans Bancorp, Inc. announced a plan to merge Evans into NBT. Evans has $2.19 billion in assets and 18 branches serving Buffalo and Rochester, Upstate New York’s two largest markets by population. Our partnership with Evans is a natural geographic extension of NBT’s footprint that complements our meaningful presence in Upstate New York. Having secured approval from our federal regulators and Evans shareholders in December 2024, we are working toward a closing and concurrent systems conversion in early May. Our integration activities with the Evans team in the months since the announcement have reaffirmed our belief that we have shared values and a relationship-based approach to serving our customers that will mesh well. We look forward to onboarding new team members and introducing customers to an expanded suite of products and services. The extension of our footprint to the west will also further align our service area with the Upstate New York Semiconductor Chip Corridor. New York has fostered an ecosystem to support the manufacturing of semiconductors and advanced electronics that extends from Buffalo to the Capital District and south into the Hudson Valley. Leading manufacturers have announced transformational investments, and NBT is well positioned to support this regional growth. Today, we have more than 60 branches located along this Chip Corridor, and that number will grow when the merger with Evans is complete. We remain committed to helping our customers and communities participate in this historic growth opportunity and continue to execute and build upon our strategies to support this initiative. The Value of Your Investment. At NBT, we don’t engage in growth for growth’s sake. We believe that every initiative we undertake is an investment in our future—whether it’s a strategic acquisition, an opportunity to expand organically with a new location or product, or the growth of our fee-based businesses. Ultimately, all these efforts are about building long- term value for our fellow shareholders as our team members support the financial service needs of our customers and communities. In 2024, we marked 12 consecutive years of annual dividend increases, affirming our ongoing commitment to delivering consistent and 12 Consecutive Years ANNUAL DIVIDEND INCREASES 5 Stock Performance favorable returns to our shareholders. We remain a strong, stable and well-capitalized company with $1.62 billion in capital at year-end. The strongest indicator of the value of your long-term investment in NBT is the consistent performance of our stock over time. For the 3-year period from December 31, 2021, to December 31, 2024, NBT’s stock price improved 24% as compared to the KBW Nasdaq Regional Banking Index (Ticker: KRX), which came in at negative 5%. Taking a longer view, for the period from year-end 2005 through year-end 2024, NBT improved 121% compared with the KRX at 25%. We appreciate your support as shareholders and the trust you place in our Executive Management Team and the Board of Directors. We extend our thanks to Jack Webb and Lowell Seifter as they retire from the Board in May. Both joined NBT in 2013 with the acquisition of Alliance Bancorp, Inc., and we are grateful for their expertise and commitment to community banking values. We will close by thanking our employees—a team that will soon be nearly 2,400 strong with the addition of new members from the Evans merger. Their commitment to serving our customers, supporting each other, and growing and evolving our business is at the heart of the value we create for you, our shareholders. Sincerely, Scott A. Kingsley Martin A. Dietrich President and Chairman of the Board Chief Executive Officer 2024 ANNUAL REPORT | 40% 30% 20% 10% 0% -10% -20% -30% -40% 12.31.2021 04.30.2022 08.31.2022 12.31.2022 04.30.2023 08.31.2023 12.31.2023 04.30.2024 08.31.2024 12.31.2024 NBTB KBW Nasdaq Regional Banking Index 6 Martin A. Dietrich Chairman of the Board John H. Watt, Jr. Vice Chairman of the Board Scott A. Kingsley President and CEO Jack H. Webb Lead Director Johanna R. Ames J. David Brown Richard J. Cantele, Jr. Timothy E. Delaney Heidi M. Hoeller Andrew S. Kowalczyk lll, Esq. V. Daniel Robinson ll Matthew J. Salanger Lowell A. Seifter, Esq. NBT Bank Honorary Directors Richard Chojnowski Patricia T. Civil James H. Douglas Daryl R. Forsythe Paul D. Horger, Esq. Janet H. Ingraham John C. Mitchell Van Ness D. Robinson Joseph A. Santangelo Paul M. Solomon Paul O. Stillman Robert A. Wadsworth Additional information regarding our Executive Management Team and Board of Directors can be found in the proxy statement for our 2025 Annual Meeting of Stockholders. Board of Directors Scott A. Kingsley President and CEO Joseph R. Stagliano Senior Executive Vice President and President of NBT Bank, N.A. Annette L. Burns Executive Vice President and Chief Financial Officer Sarah A. Halliday Executive Vice President and President of Commercial Banking Shauna M. Hyle Executive Vice President, Retail Community Banking Ruth H. Mahoney Executive Vice President and President of Wealth Management Cynthia A. Smaniotto Senior Vice President and Chief Human Resources Officer M. Randolph Sparks Executive Vice President, General Counsel, Chief Ethics Officer and Corporate Secretary Amy Wiles Executive Vice President, Chief Credit Officer and Chief Risk Officer Executive Management Team Operating Committee The following NBT leaders serve on the Operating Committee with the Executive Management Team and Regional Leadership. Leonard P. Chinski SVP and Chief Audit Officer Jeffrey S. Delepine II SVP and Senior Director of Enterprise Risk Management Kurt T. Edwards SVP and Chief Consumer and Business Banking Credit Officer Kenneth J. Entenmann, cfa® SVP, Chief Investment Officer and Chief Economist Amy S. Hurta SVP and Senior Director of Operations David Krupski SVP and Commercial Chief of Staff Tucker H. Lounsbury, cic President, NBT Insurance Agency Joseph M. Ondesko SVP and Corporate Treasurer Manuel S. Orta SVP and Director of Business Development, Wealth Management Karen A. Sastri VP and Chief Diversity Officer Joseph P. Sergienko SVP and Managing Director of Enterprise Risk Thomas M. Sutton SVP and Director of Retail Banking Tara F. Trafton SVP and Chief Commercial Credit Officer Kimberly J. Twitchell SVP and Senior Director of Affordable Housing EPIC Retirement Plan Services Manuel Marques, cpc, qpa, qka, qpfc, aif® President NBT Insurance Agency Tucker H. Lounsbury, cic President | NBT BANCORP INC. Leadership Regional Leadership Central New York & Pennsylvania David A. Kavney, President Binghamton Jeffrey D. Lake Regional President Pennsylvania Matthew K. Colgan Regional Commercial Banking Manager Southern Tier Jennifer R. Telesky Regional Commercial Banking Manager Central New York & Mohawk Valley David A. Kavney Regional President Eastern New York & Connecticut Alfred V. Testa, President Hudson Valley John M. Davies Regional President Connecticut Andreas A. Kapetanopoulos Regional President Glens Falls Marc J. Monahan Regional Executive Capital Region & North Country Alfred V. Testa Regional President New England Michael P. O’Reilly, President New Hampshire Justin L. Jennings Regional President Vermont & Massachusetts Daniel P. Werme Regional President Maine Michael P. O’Reilly Regional President 7 Shareholder Information Corporate Headquarters NBT Bancorp Inc. 52 South Broad Street Norwich, NY 13815 800.NBT.BANK Independent Auditors KPMG LLP 515 Broadway Albany, NY 12207 Financial Reports and Releases Copies of the Company’s annual report to the Securities and Exchange Commission on Form 10-K, quarterly reports on Form 10-Q, and news releases may be obtained without charge by visiting our website at www.nbtbancorp.com or by writing to the attention of our Chief Financial Officer at the corporate headquarters address. Investor Relations Information regarding the Company, our dividend reinvestment and stock purchase plan, and direct deposit of dividends can be found on our website at www.nbtbancorp.com. Those seeking additional information may contact us by phone at 800.NBT.BANK (800.628.2265, Option 7) or by mail at the corporate headquarters address. Stock Transfer and Registrar Agent Equiniti Trust Company, LLC 55 Challenger Road, Floor 2 Ridgefield Park, NJ 07660 800.NBT.BANK (800.628.2265, Option 7) www.equiniti.com helpast@equiniti.com NBTB Nasdaq Global Select Market 2024 ANNUAL REPORT | Forward-Looking Statements This letter contains statements that constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and are subject to a number of risks and uncertainties. Such statements are not guarantees of future performance and actual results may differ materially from any forward-looking statements contained in this letter. For a discussion of the factors that might cause such differences, please refer to our filings with the Securities and Exchange Commission. 2025 Annual Meeting Tuesday, May 20, 2025 | 10:00 a.m. ET www.virtualshareholdermeeting.com/NBTB2025 www.nbtbancorp.com