Community Bank System (CBU) 8-K Regulation FD Disclosure

Exhibit 99.1

Investor Day 2024

‐ ‐ Disclaimers

Welcome & Opening Remarks • • • • •

Investor Day Agenda

Investor Day Speakers

Company Overview & Investment Thesis

Company Overview • • • • • • •

About CBU • • • • • • • • • • • • • • • •

How We Operate: Our Core Values

Our Evolution Into a Diversified Financial Company • • • • •

Our Investment Thesis: • • • • • •

Below Average Risk

Above Average Returns

Our System Produces Premium Results 10Yr Avg. Relative Premium to KRX (median): 4.2x 5Yr Avg. Relative Premium to KRX (median): 6.1x Current Relative Premium to KRX (median): 5.0x

Our Opportunity Set: Banking (CBNA) 2023 Summary of Deposits $ in Millions Buffalo, NY MSA Rochester, NY MSA Syracuse, NY MSA Albany, NY MSA Deposit Market Size: $76,153 $32,626 $18,975 $47,811 Market 5-Year CAGR: 11.8% 7.4% 6.4% 16.1% CBNA Deposits: $237 $813 $1,052 $183 CBNA Market Share: 0.3% 2.5% 5.5% 0.4% CBNA 5-Year CAGR: 12.6% 14.1% 4.9% 1.0% CBNA Branches: 3 12 14 6 CBNA De Novo: 3 3 4 3 2023 Summary of Deposits $ in Millions Allentown, PA MSA Springfield, MA MSA Manchester NH, MSA Total Selected MSAs Deposit Market Size: $25,180 $15,924 $18,790 $235,459 Market 5-Year CAGR: 11.6% 6.5% 7.1% 10.6% CBNA Deposits: $62 $31 $0 $2,378 CBNA Market Share: 0.3% 0.2% 0.0% 1.0% CBNA 5-Year CAGR: 6.6% (3.6%) NA 7.6% CBNA Branches: 2 1 0 38 CBNA De Novo: 3 1 1 18 #1 or #2 deposit market share position in 66% of the towns we do business in

Our Opportunity Set: Employee Benefit Services (BPAS) Industry Note 5: There are over 111 million benefit plan participants in the United States BPAS 10Yr Operating Revenue CAGR2 :12.1% 5Yr Operating Revenue CAGR2 : 5.9% 3Yr Operating Revenue CAGR2 : 6.1% 880,000+ 6 Top 5

Our Opportunity Set: Insurance Services (OneGroup) OneGroup 7Yr Operating Revenue CAGR3 : 9.8% 5Yr Operating Revenue CAGR3 : 8.6% 3Yr Operating Revenue CAGR3 : 13.9% Top 5 13 66th Industry Note 6: The top 75 insurance agencies have grown revenue at a 13% CAGR (2019 – 2022)

Wealth 10Yr Operating Revenue CAGR2 : 8.3% 5Yr Operating Revenue CAGR2 : 6.1% 3Yr Operating Revenue CAGR2 : 3.6% Our Opportunity Set: Wealth Management Services $12.5B 15.4%

Consistently Improving Productivity 5Yr Op. Rev / FTE CAGR2 : 4.6% 5Yr Op. Rev / FTE CAGR2 : 1.6% 5Yr Op. Rev / FTE CAGR2 : 5.5% 5Yr Op. Rev / FTE CAGR2 : 3.4%

How Our System Works • • Banking • • • • • • • Insurance Wealth Benefits • Insurance Wealth Banking Our Community Our Financial Solutions Our System • • • Benefits

• Local Growth Opportunities • • • • • • U.S. Avg: 1.60% > 2.5% 1.5% - 2.5% 0% - 1.5% < 0% Non-MSA; excluded

Banking

Banking • • • • • • •

CBNA at a Glance • • • • • • • Ranked as one of America’s most trustworthy banks of 2023 by Newsweek

Liquidity & Credit Are Our Foundational Strengths • • • 2 2

We Have Grown Net Interest Income Every Year Since 2006

Business Line Summary • • • • • • • • • •

Loan Portfolios & Asset Quality

Our Banking Evolution ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪

De-centralized Regional Structure

Established Growth Capabilities Across All Regions

Retail & Business Banking • • • • • • • • • • • •

Optimizing Delivery Channels for Growth • • • •

• • • • • • • • • Digital Banking Capabilities

Consumer Lending • • • • • • • • • • •

• • • • • • Consumer Lending

Commercial Banking

Commercial Lending 0.07% 10-year average net-charge off ratio (2014-2023) NOO CRE represents 197% of total bank-level capital compared to the KRX bank-held median of 242%

Commercial Banking Initiatives • • • • • • • • • • • •

Expansion Markets Opportunity 2023 Summary of Deposits $ in Millions Buffalo, NY MSA Rochester, NY MSA Syracuse, NY MSA Albany, NY MSA Allentown, PA MSA Springfield, MA MSA Manchester NH, MSA Deposit Market Size: $76,153 $32,626 $18,975 $47,811 $25,180 $15,924 $18,790 Market 5-Year CAGR: 11.8% 7.4% 6.4% 16.1% 11.6% 6.5% 7.1% CBNA Deposits: $237 $813 $1,052 $183 $62 $31 $0 CBNA Market Share: 0.3% 2.5% 5.5% 0.4% 0.3% 0.2% 0.0% CBNA 5-Year CAGR: 12.6% 14.1% 4.9% 1.0% 6.6% (3.6%) NA CBNA Branches: 3 12 14 6 2 1 0 CBNA De Novo: 3 3 4 3 3 1 1 #1 Market Share Company: M&T Bank Corp. ESL FCU M&T Bank Corp. Citizens Financial Group Inc. Wells Fargo & Co. Peoples Bancorp Citizens Financial Group Inc. 2023 Market Share: 65.4% 17.2% 19.5% 23.6% 16.2% 14.3% 24.2% Top 3 Institution Market Share: 79.6% 40.4% 46.8% 55.5% 35.2% 38.8% 61.8% Top Non-Super Regional, Non-Credit Union Market Share: Northwest Bancshares, Inc. Canandaigua National Corp. NBT Bancorp Inc. TrustCo Bank Corp NY Fulton Financial Corp Peoples Bancorp Primary Bank 2023 Market Share: 3.2% 11.0% 6.8% 7.2% 7.3% 14.3% 3.1%

Expansion Markets

What the Future Brings

Employee Benefit Services

Employee Benefit Services • • • • • • •

One Company, One Call • • • • • • • •

BPAS at a Glance

Our History

Well Positioned For Success in a Growing Industry

Business Line Summary • • • • • •

Revenue Model & Performance 10Yr Operating Revenue CAGR1,4: 12.1% 3Yr Avg. Operating Margin3,5: 42.9% TTM Revenue by Source 51% asset-based 45% fee-based 4% other

Recordkeeping & TPA • • • • • • • • • • • • • •

How We Win in Recordkeeping • • • • • • • • • • • • •

State of the Art Technology

Other Revenue Verticals • • • • • • • • • • • • • • • • • • • • • • • •

CIT Fund Administration BPAS is one of the three largest special purpose trust companies focused on collective funds3 • • • • • • • Industry Note: Morningstar notes that CITs now represent 49% of total DC plan assets and will overtake mutual funds this year as the most popular target-date vehicle 2

Future Outlook

Insurance Services

Insurance Services • • • • • •

Insurance Services • • • • • • • • • • • •

OneGroup at a Glance

• • • • Insurance Brokerage Industry

Favorable Business Mix With Deep Specialties

Lines of Business • • • • • • • • • •

Revenue Performance 7Yr Operating Revenue CAGR1,4: 9.8% 3Yr Avg. Operating Margin3,5: 18.8%

Carrier Depth • •

Future Outlook

Wealth Management Services

Wealth Management Services • • • • •

Wealth Management Services • • • • • • • • • • •

Well Positioned For Success in a Growing Industry

Uniquely Broad and Deep Capabilities • • • • • • • • • • • • • • • • • •

Trended Results

Wealth Management Services: Financial Performance 10Yr Operating Revenue CAGR1,4: 8.3% 3Yr Avg. Operating Margin3,5: 31.2%

Future Outlook

Risk Management

Risk Management • • • • • • •

Risk Management Framework

CBNA’s Lending Philosophy & Credit Risk Management

Debt-to-Income Ratio

Loan Losses

Loan Mix Comparison

Retail Lending

Funding Metrics

Deposit Granularity $17 $32 $0 $100 $200 $300 $400 $500 $600 CBNA Industry Thousands Average Deposit Account Balance $201 $508 $1,120 $0 $200 $400 $600 $800 $1,000 $1,200 First Republic Signature SVB Thousands Average Deposit Account Balance

Financial Performance

Financial Performance • • • • • • • •

Fundamental Elements of Our Enduring Success

• • Focus on Revenue Quality, Diversification and Sustainable Results

Strong Asset Quality

Allowance Industry Comparison

• • • • • Core Deposit Strength 22% cycle to date deposit beta1 24% cycle to date funding beta1 30% cycle to date interest-bearing deposit beta1

Liquidity Position & Sources • • • • •

• • Solid Capital Position

Outperformance During Turbulence

Company Performance 9.3% 4.5% 1.29% 40% $1.29 0.06% $0.95 0.05%

Segment Performance 10Yr Operating Revenue CAGR3 : 12.1% 3Yr Avg. Operating Margin4 : 42.9% 10Yr Operating Revenue CAGR3 : 5.4% 3Yr Avg. Operating Margin4 : 38.9% 7Yr Operating Revenue CAGR3 : 9.8% 3Yr Avg. Operating Margin4 : 18.8% 10Yr Operating Revenue CAGR3 : 8.3% 3Yr Avg. Operating Margin4 : 31.2%

Capital Deployment Since 12/31/2018 46.5% operating payout ratio 53.1% payout ratio

Catalysts for Earnings Growth & Shareholder Value Creation

• • Loan Repricing Opportunity 28% of outstanding loan balances are expected to reprice or be repaid in the next 12 months1

• • Securities Redeployment Opportunity

Opportunities and Financial Targets • • • • • • • • • • •

Valuation Considerations

Valuation Considerations 10Yr Avg. Relative Premium to KRX (median): 4.2x 5Yr Avg. Relative Premium to KRX (median): 6.1x Current Relative Premium to KRX (median): 5.0x

P/E Reference Framework

5Yr Avg 10Yr Avg KRX (median): 1.52x 1.71x KRX (top quartile): 1.80x 2.05x Illustrative P/TBV Context

Closing Remarks

Closing Remarks ▪ ▪ ▪ ▪ ▪ ▪

Thank you!

Appendix

Glossary of Terms

Primary Subsidiaries

Board of Directors

KRX Peer Group

Multifamily & NOO CRE by Location

• • • • Reconciliation of GAAP and Non-GAAP

Pre-tax, Pre-provision Components

Operating Net Income

Net Interest Margin & Operating ROA

Operating Revenues

Equity-to-Assets

Book Value

Operating Noninterest Expenses

Core Results