Banks lend out most of the money you deposit, keeping only a small fraction in reserve

When you put money in a checking or savings account, the bank does not lock it in a vault with your name on it. Instead, the bank uses your deposit to make loans to other customers and businesses. The bank keeps a percentage in reserve—the amount varies by account type and is set partly by federal rules—and lends the rest to borrowers who pay interest. That interest income is how banks pay you interest on savings accounts, cover their operating costs, and generate profit.

This system is called fractional reserve banking. It works because not every depositor withdraws their money at the same time. The bank counts on steady deposits flowing in while others flow out. Your money is insured by the Federal Deposit Insurance Corporation (FDIC) up to $250,000 per account type per bank, so even if the bank fails, you get your money back up to that limit.

Key Takeaways

  • Banks lend out the majority of customer deposits to borrowers, keeping only a required reserve amount on hand.
  • The interest you earn on savings comes from the interest borrowers pay the bank on loans.
  • FDIC insurance protects your deposits up to $250,000 per account type at each bank, even if the bank fails.
  • Banks also invest deposits in bonds and other securities, which generates additional income beyond lending.
  • The difference between what banks pay you and what they charge borrowers is their primary source of profit.

How banks decide how much to lend versus how much to keep

Federal banking regulators require banks to hold a minimum amount of capital and liquid reserves. The exact percentage depends on the size of the bank and the type of deposit. For most checking and savings accounts, banks must keep a smaller reserve than they do for other types of accounts. This reserve requirement ensures the bank can handle customer withdrawals on any given day without running out of cash.

Beyond the legal minimum, banks decide their own reserve levels based on how much cash they expect to need. A bank that sees steady deposits and predictable withdrawals can lend out a higher percentage. A bank in a region with economic uncertainty might keep more in reserve. Banks also use computer models to forecast cash flow and adjust their lending accordingly.

Where your money goes: loans to individuals and businesses

The largest use of customer deposits is personal lending. Banks make mortgage loans to homebuyers, auto loans to car buyers, and personal loans to consumers. Each of these loans generates interest income for the bank. A homebuyer might pay 6 to 7 percent interest on a mortgage; the bank may have paid you 4 percent on your savings account. That 2 to 3 percent difference, multiplied across thousands of loans, is a major source of bank profit.

Banks also lend to businesses—small businesses getting lines of credit, large corporations financing expansion, and commercial real estate developers building office parks and shopping centers. Business loans typically carry higher interest rates than consumer loans because they carry more risk. If a business fails, the bank loses money; if a homeowner defaults, the bank can foreclose on the house.

Credit card lending is another major category. When you use a credit card, you are borrowing from the card issuer, which is often a bank. The bank pays the merchant immediately and collects the debt from you later, plus interest and fees. Credit card interest rates are typically much higher than mortgage rates—often 18 to 25 percent—because credit card debt is unsecured (the bank has no collateral to seize if you do not pay).

Investments banks make with deposits

Banks do not lend out every dollar they receive. They also invest deposits in bonds, Treasury securities, and other financial instruments. A bank might buy U.S. Treasury bonds, which are considered very safe because they are backed by the federal government. The bank earns interest on these bonds, which is another revenue stream. During periods when loan demand is low, banks shift more deposits into securities to keep the money working.

Some banks invest in mortgage-backed securities—bundles of home loans sold by other lenders. This creates a chain: you deposit money at Bank A, Bank A buys mortgage-backed securities from Bank B, and Bank B uses that money to fund mortgages. The system is designed so money flows to wherever it is needed, but it also means your deposit can be tied up in loans you never directly made.

How banks pay you interest and cover their costs

The interest you earn on a savings account or money market account comes directly from the interest borrowers pay on loans. If the bank earns 6 percent on a mortgage and pays you 4 percent on savings, the bank keeps 2 percent. On a $100,000 deposit, that means the bank makes $2,000 per year from your money alone (before accounting for the cost of servicing your account).

Banks also charge fees to cover costs: monthly account maintenance fees, overdraft fees, wire transfer fees, and ATM fees. These fees pay for the physical branches, the employees, the technology infrastructure, and the regulatory compliance required to operate a bank. A large bank might have thousands of employees, hundreds of branches, and millions of dollars in annual technology spending.

Interest rates on savings accounts fluctuate based on what the Federal Reserve does. When the Fed raises its benchmark interest rate, banks can charge more on loans, so they can afford to pay more on savings accounts. When the Fed lowers rates, savings account interest rates drop too. This is why your savings account paid almost nothing during 2020 and 2021, and why rates rose starting in 2022.

What happens if too many people withdraw money at once

If a large number of depositors try to withdraw their money at the same time—an event called a bank run—the bank may not have enough cash on hand because most of the money is out on loan. The bank can borrow from other banks or from the Federal Reserve's discount window to cover the withdrawals, but if the panic spreads and the bank cannot borrow enough, it can fail.

This is why FDIC insurance exists. When a bank fails, the FDIC steps in, takes over the bank's assets, and pays depositors up to $250,000 per account. The FDIC has a fund built from fees paid by banks, so the cost does not fall on taxpayers. Bank runs are rare in modern times because of FDIC insurance and because regulators monitor banks closely for signs of trouble.

How banks manage risk when lending your money

Banks use several tools to reduce the risk that borrowers will not repay loans. For mortgages, the house itself is collateral—if you stop paying, the bank forecloses and sells the house. For auto loans, the car is collateral. For unsecured loans like credit cards and personal loans, banks rely on credit scores, income verification, and the borrower's history of repayment.

Banks also diversify their lending. A bank that lends only to one industry or one geographic region is vulnerable if that industry or region enters a recession. A bank that spreads loans across many industries, regions, and borrower types is more resilient. Banks also sell some loans to other investors—a process called loan securitization—which transfers some of the risk away from the bank.

Despite these safeguards, banks do experience loan losses. Some borrowers default, and the bank writes off the debt as a loss. Banks set aside reserves for expected losses based on historical data. If losses exceed the reserve, the bank's profit declines. In severe recessions, loan losses can be large enough to threaten a bank's solvency.

Frequently Asked Questions

Can a bank go bankrupt and take my money with it?

No. The FDIC insures deposits up to $250,000 per account type per bank. If your bank fails, the FDIC pays you the full amount of your insured deposits. You may have to wait a few days for the transfer to a new bank, but you will not lose money. If you have more than $250,000 at one bank, the amount over $250,000 is not insured, so consider splitting large balances across multiple banks.

Why do banks pay such low interest on savings accounts?

Banks pay low interest because they can. When interest rates set by the Federal Reserve are low, banks have less incentive to compete for deposits by offering high rates. When Fed rates are high, savings account rates rise. Banks also pay low rates because they have many sources of income beyond savings account interest—fees, investment income, and lending profit all contribute to the bottom line.

What happens to my money if I close my account?

When you close an account, the bank returns your balance to you in full (assuming it is under $250,000). The bank stops using your money for loans and investments. If you have outstanding checks or automatic payments, those will be processed before the account closes. Make sure to redirect direct deposits and cancel automatic payments before closing the account.

Do banks invest my money in the stock market?

Most banks do not invest customer deposits directly in stocks. They invest primarily in bonds, Treasury securities, and other fixed-income instruments, which are considered safer. However, some banks offer brokerage services where you can invest in stocks yourself, and some offer investment advisory services. These are separate from your deposit account and carry different risks.

How much of my deposit does a bank actually lend out?

The percentage varies by bank and account type, but a typical bank lends out 80 to 90 percent of deposits and keeps 10 to 20 percent in reserve. The exact amount depends on federal reserve requirements, the bank's own risk management, and current economic conditions. During recessions, banks tend to keep higher reserves and lend less. During economic expansions, they lend more aggressively.