Banks make money from deposits by putting your cash to work the moment it lands in your account. They lend it out at interest rates far higher than what they pay you, invest the surplus in government and mortgage-backed securities, earn interest by parking reserves at the Federal Reserve, collect a small fee every time you swipe your debit card, and charge account fees on top. The gap between what a bank pays depositors and what it earns deploying their money is the core of how the business works.
The Interest Spread Is the Main Engine
The biggest source of profit is the difference between the interest a bank pays you and the interest it charges borrowers. In early 2026, the national average savings account paid roughly 0.39% APY, while the average personal loan from a commercial bank carried a rate around 12%. The bank keeps the difference, minus operating costs.
Measured across all of a bank’s loans and investments, that gap is called the net interest margin. Industry-wide, it stood at 3.39% in the fourth quarter of 2025, with community banks running slightly higher at 3.77%.1FDIC.gov. FDIC Quarterly Banking Profile Fourth Quarter 2025 Most commercial banks target somewhere between 3% and 4%.
The strategy works because of a timing mismatch. You can pull money out of a checking account any day, but the bank lends that money out for years at a time: a five-year auto loan, a thirty-year mortgage. Interest starts accruing on those loans immediately, and most are backed by collateral such as a home or vehicle, giving the bank a fallback if a borrower stops paying.
How much of each deposit is available for lending? Under current Federal Reserve rules, the reserve requirement is zero percent across all deposit tiers.2eCFR. 12 CFR Part 204 – Reserve Requirements of Depository Institutions (Regulation D) Banks still keep an operating cushion to cover daily withdrawals, but everything above that cushion is capital the bank can deploy. If the cost of attracting deposits climbs faster than income from loans, the margin shrinks and profitability suffers, which is why banks watch their deposit rates closely.
Interest From the Federal Reserve
Banks also earn money by simply leaving cash at the Federal Reserve. Federal law authorizes the Fed to pay interest on balances that banks hold in their reserve accounts,3Office of the Law Revision Counsel. 12 USC 461 – Reserve Requirements and as of early 2026 that rate is 3.65%.4Federal Reserve Board. Implementation Note Issued January 28, 2026 – Decisions Regarding Monetary Policy Implementation
This gives a bank a risk-free way to earn income on deposits it is not currently lending. When loan demand slows, or when a bank simply wants to hold extra cash for safety, it can still generate a return by leaving the money at the Fed. The rate also sets a floor for lending decisions. A bank has little reason to make a risky loan at 3% when it can earn 3.65% with zero risk.
Investing Deposits in Securities
When a bank has more deposits than it can profitably lend to individual borrowers, it becomes an institutional investor. Banks buy low-risk, interest-bearing securities that generate steady income: U.S. Treasury bonds backed by the federal government, municipal bonds issued by local governments, and mortgage-backed securities that bundle home loans into a single instrument paying regular principal and interest. These typically yield more than banks pay depositors, so the spread still works in the bank’s favor.
Diversifying across bond types limits the damage any single default can cause. Investment income also helps banks maintain the capital levels regulators require to be considered well-capitalized.5Federal Register. Regulatory Capital Rule – Revisions to the Community Bank Leverage Ratio Framework
Debit Card Swipes
Every time you swipe or tap a debit card linked to your deposit account, the bank earns a small fee from the merchant’s payment processor. Card networks set these interchange fees, but federal rules cap what large banks can charge. For banks with $10 billion or more in assets, the maximum is 21 cents plus 0.05% of the transaction value, with an additional 1 cent allowed for fraud prevention.6eCFR. 12 CFR Part 235 – Debit Card Interchange Fees and Routing (Regulation II) Smaller banks are exempt from the cap and typically earn more per transaction.
On a $50 purchase at a covered bank, the interchange fee would be roughly 24 cents. Multiply that across millions of daily transactions and the revenue adds up. This is one reason banks push you to use your debit card, and why some waive monthly fees when you hit a set number of transactions. Every swipe generates income that cash and paper checks do not.
Account Fees
Banks collect a range of fees directly tied to maintaining your account. This non-interest income keeps flowing regardless of where interest rates sit.
- Monthly maintenance fees, typically $5 to $25, often waived if you keep a minimum balance or receive direct deposits.
- Overdraft fees, around $35 per occurrence at most large banks.
- Out-of-network ATM fees, several dollars per withdrawal, sometimes charged by both your bank and the ATM operator.
- Stop-payment fees, roughly $15 to $36 when you ask the bank to block a check you have written.
- Paper statement fees, a few dollars a month if you opt out of electronic statements.
These charges act as an income floor. When low interest rates squeeze the net interest margin, fee income keeps the deposit relationship profitable.
What It Costs the Bank to Hold Your Money
Taking in deposits is not free. Every federally insured bank pays premiums to the Federal Deposit Insurance Corporation to maintain the fund that protects depositors up to $250,000 per person, per bank, per ownership category.7FDIC.gov. Your Insured Deposits Premiums scale with how much insured deposits a bank holds and how risky regulators consider it to be.
Assessment rates for well-rated, established banks run about 2.5 to 18 basis points a year, or roughly 2.5 to 18 cents for every $100 in deposits. Banks with weaker regulatory ratings or more complex operations can pay up to 42 basis points.8FDIC.gov. FDIC Assessment Rates The FDIC has set its target reserve ratio for the insurance fund at 2% of all insured deposits for 2026.9Federal Register. Designated Reserve Ratio for 2026
A bank paying 10 basis points in FDIC premiums while earning a 3.39% net interest margin still keeps most of the spread, but insurance is a fixed overhead that grows with the deposit base. Holding a strong regulatory rating is one of the most effective ways a bank can hold down that cost, which is why compliance and risk management get so much attention inside the industry.