Banks make a profit primarily by paying depositors low interest rates and lending the same money out at much higher rates, keeping the difference. That spread, known as the net interest margin, generates roughly 60% of revenue at a typical U.S. commercial bank. The remaining 40% comes from account and transaction fees, card interchange, loan sales, servicing income, and wealth management. Understanding how banks make a profit means looking at each of those streams and at the costs that eat into them.
The Interest Rate Spread
The core of banking is simple arithmetic. A bank might pay 0.01% on a basic savings account, or up to 4% on a competitive certificate of deposit. It then lends that money at rates several times higher. A 30-year fixed mortgage averaged around 6% in early 2026, and a two-year personal loan from a commercial bank ran about 11.65%.1Freddie Mac. Mortgage Rates2Federal Reserve Bank of St. Louis. Finance Rate on Personal Loans at Commercial Banks, 24 Month Loan Credit cards produce the widest margins by far, with average APRs reaching 22.8% by 2023 after nearly doubling over the previous decade.3Consumer Financial Protection Bureau. Credit Card Interest Rate Margins at All-Time High
A gap of a few percentage points doesn’t sound dramatic on its own. Applied across billions of dollars in loans and millions of accounts, it produces enormous income.
The size of that gap depends heavily on the Federal Reserve. When the Fed raises its target rate, banks tend to increase what they charge on new loans faster than they raise what they pay on deposits, temporarily widening the spread. When rates fall, loan yields drop while deposit costs adjust down more slowly.4Board of Governors of the Federal Reserve System. Changes in Monetary Policy and Banks Net Interest Margins
Not every loan gets repaid, and banks have to plan for that. Regulators require an allowance for credit losses, a reserve set aside for expected defaults. When a bank expects more borrowers to fall behind, it books a larger provision expense, which reduces reported profit before any actual loss occurs.5Office of the Comptroller of the Currency. Allowances for Credit Losses Credit scoring, debt-to-income analysis, and collateral requirements exist to keep those losses manageable.
Account and Transaction Fees
Fees charged directly to customers give banks a steady income stream that doesn’t move with interest rates. Monthly maintenance charges on checking and savings accounts run anywhere from about $5 to $35, though most banks waive them for customers who keep a minimum balance or set up direct deposit. Outgoing domestic wire transfers typically cost $25 to $35 each.
Overdraft and non-sufficient funds fees have long been among the most profitable charges banks collect, historically running around $35 per transaction.6FDIC. Overdraft and Account Fees That picture has changed. Several large banks have voluntarily cut overdraft fees to $10 or $15, and some have eliminated NSF fees entirely. Bank of America’s overdraft revenue fell 91% after it lowered the fee to $10 and dropped NSF fees.7Consumer Financial Protection Bureau. Overdraft/NSF Revenue in 2023 A CFPB rule that would have capped overdraft fees at $5 for large banks was repealed under the Congressional Review Act in 2025 before it took effect, but competitive pressure has kept fees moving down at most major institutions anyway.
Using an out-of-network ATM triggers two charges: a surcharge from the ATM owner and a fee from your own bank for going outside its network. Combined, these average close to $5 per withdrawal. Paper statements, cashier’s checks, and account dormancy add smaller amounts. None of these charges is large on its own, but multiplied across millions of accounts they produce billions in annual non-interest income.
Card Interchange
Every card swipe sends a small fee to the bank that issued the card, paid by the merchant. Most consumers never see it, which makes interchange one of the quietest revenue streams in banking. Credit card interchange typically runs from roughly 1% to nearly 3% of the purchase, depending on the network, card type, and merchant category.
Debit interchange is lower because federal law caps it. The Durbin Amendment directs the Federal Reserve to ensure debit interchange fees are “reasonable and proportional” to the issuer’s costs.8Office of the Law Revision Counsel. 15 USC 1693o-2 – Reasonable Fees and Rules for Payment Card Transactions Under the Fed’s implementing rule, covered issuers cannot collect more than 21 cents plus 0.05% of the transaction value, with a possible 1-cent fraud-prevention adjustment.9Board of Governors of the Federal Reserve System. Regulation II – Average Debit Card Interchange Fee by Payment Card Network On a $50 debit purchase, that works out to about 24 cents.
Small numbers scale. Large card issuers process billions of transactions a year, and credit interchange in particular funds the generous rewards programs banks offer, because those rewards still cost less than the interchange they bring in.
Selling and Servicing Loans
Banks don’t always keep the loans they write. A bank might originate a mortgage on Monday and sell it to an investor or a government-sponsored entity like Fannie Mae by Friday, booking an immediate gain on sale. Residential mortgages drive most of this income across the industry, and gain-on-sale margins for mortgage lenders typically run 2% to 2.5% of the loan amount.
Selling a loan doesn’t end the bank’s relationship with it. Banks often keep the servicing rights, meaning they continue to collect the monthly payment, run the escrow account, and handle customer service in exchange for a recurring fee.10FDIC. Mortgage Servicing Rights Sales That’s why the company you send your mortgage payment to isn’t always the one that wrote the loan. Servicers earn a small percentage of the outstanding balance each year without carrying default risk on their balance sheet, and mortgage servicing rights are valuable enough that they trade as standalone assets.
Wealth Management and Advisory Fees
Investment advisory and wealth management divisions charge fees based on portfolio size instead of lending activity. Annual management fees for retail clients typically range from 0.50% to 1.50% of assets under management, with the percentage falling as the account grows. Institutional clients pay less, averaging around 0.24%. A bank managing $100 billion in client assets at an average fee of 0.75% produces $750 million a year from that business line before expenses.
Banks also collect commissions by selling insurance, annuities, and brokerage products through their branches, generating one-time revenue at the point of sale and, in many cases, ongoing trail fees. The customer who opens a checking account becomes a candidate for a retirement plan or life insurance policy, and banks with large retail networks have the biggest advantage here. Fee-based advisory income also reduces a bank’s dependence on interest rates, which is why most large banks have expanded these divisions heavily over the past two decades.
Business Banking and Treasury Services
Commercial customers generate some of the highest revenue per account. Beyond loans and lines of credit, banks charge corporate clients for payroll processing, lockbox collections, cash vault deposits, fraud detection, and ACH payment setup. Priced per transaction or as monthly flat fees, these services can run into thousands of dollars a month for a large company with complex cash flows.
Small business accounts also carry higher fee schedules than personal accounts, with maintenance charges, per-check fees, and cash-handling surcharges that reflect the extra work involved. Business deposits then feed back into the lending side of the bank as a large pool of low-cost funding. Companies get the cash management infrastructure they need, and banks get cheap deposits to lend.
What It Costs to Run a Bank
Revenue only becomes profit after expenses, and banks are expensive to operate. The standard measure of cost discipline is the efficiency ratio, which divides operating expenses by total revenue. As of late 2025, the average U.S. commercial bank posted an efficiency ratio around 56%, meaning about 56 cents of expense for every dollar of revenue. Anything below 50% is considered excellent.
Employee compensation is the single largest cost, at roughly half of operating expenses. Technology and data processing is the fastest-growing category, driven by spending on mobile platforms, cybersecurity, and fraud prevention. Branch and office space, legal and compliance work, and marketing round out the major line items. Smaller banks generally run higher efficiency ratios because they can’t spread fixed costs across as many accounts, one reason the industry has been consolidating for decades.
A bank with a strong interest margin but sloppy operations can post lower profits than a leaner competitor with narrower margins. The most profitable banks combine a wide interest spread, healthy fee and interchange income, diversified advisory revenue, and tight cost control. That combination is harder to hit than it looks, which is why profitability varies so widely across the industry.