Banks pay interest by calculating a percentage of your account balance and depositing that amount into your account on a set schedule

Interest is money the bank pays you for letting them use your deposits. The bank lends your money to other customers through mortgages, car loans, and business lines of credit. They keep the difference between what they pay you and what they charge borrowers. The amount you earn depends on three things: your balance, the interest rate the bank offers, and how often the bank compounds interest—meaning how often it calculates interest on your balance plus any interest already earned.

Most savings accounts pay interest monthly, though some pay daily, quarterly, or annually. When the bank pays interest, it deposits the amount directly into your account. That new balance then earns interest in the next period, which is why accounts with more frequent compounding grow faster over time.

Key Takeaways

  • Banks calculate interest as a percentage of your balance and pay it on a schedule—usually monthly—by depositing money into your account.
  • The Annual Percentage Yield (APY) tells you the real rate you'll earn per year when compounding is included, and it's the number to compare between banks.
  • Daily compounding grows your money faster than monthly compounding because interest starts earning interest sooner.
  • Your actual interest payment changes every period because it's calculated on your current balance, which may be higher or lower than the previous month.

Understanding APY versus interest rate

Banks advertise two different numbers: the interest rate and the Annual Percentage Yield (APY). The interest rate is the percentage the bank applies to your balance. The APY is the real yearly return you'll get after compounding is factored in. APY is always equal to or higher than the interest rate because it includes the effect of earning interest on your interest.

For example, a bank might offer a 4.50% interest rate compounded daily. When you calculate the effect of daily compounding over a full year, the actual return is 4.60% APY. The difference is small in this case, but it matters when you're comparing accounts. Always compare APY numbers between banks, not interest rates, because APY shows you what you'll actually earn.

How compounding frequency changes what you earn

Compounding is the schedule on which the bank calculates and adds interest to your account. The more often interest compounds, the more you earn, because each time the bank adds interest, that new amount starts earning interest too.

A savings account with $10,000 at 4.50% APY will earn roughly $450 in a year. But the path to that $450 differs based on compounding. With daily compounding, the bank calculates interest 365 times per year and adds small amounts each day. With monthly compounding, it calculates 12 times per year and adds larger amounts each month. With annual compounding, it calculates once and adds the full amount at year-end. The daily version grows slightly faster because interest starts working for you immediately, but the difference over one year is usually just a few dollars on a typical balance.

The difference becomes more noticeable over many years or with large balances. A $100,000 account earning 4.50% APY will gain roughly $4,500 per year, and the compounding method will make a bigger difference in the total.

When and how the bank deposits your interest

The bank deposits interest into your account on a regular schedule. Most banks pay monthly, on the same date each month or on the last business day of the month. Some high-yield savings accounts pay daily or weekly. A few older accounts may still pay quarterly or annually, though this is less common now.

You'll see the deposit in your account balance and in your transaction history. The bank does not send you a separate check or transfer—the interest simply appears as a deposit from the bank itself. If you have automatic transfers set up, they happen after the interest is deposited, so your balance includes the interest earned.

Why your interest payment changes month to month

Your interest payment is not the same every month because it's calculated on your current balance. If you deposit $5,000 in the middle of the month, the interest calculation for that month may only include part of that deposit. If you withdraw $3,000 before the interest calculation date, you earn less interest that month.

Banks calculate interest on your average daily balance or your ending balance, depending on the account. Average daily balance means the bank adds up your balance for each day of the month and divides by the number of days. Ending balance means the bank uses only your balance on the calculation date. Your account agreement or the bank's website will tell you which method they use. Average daily balance is more common and usually more favorable to you because it counts deposits you made partway through the month.

How interest rates change and what that means for you

Banks change their interest rates based on what the Federal Reserve does with its benchmark rate. When the Fed raises rates, banks usually raise savings account rates within days or weeks. When the Fed cuts rates, banks cut savings account rates, though sometimes more slowly. Your rate can change at any time unless you have a fixed-rate account, which is rare for savings accounts.

If your rate drops, your interest payment drops too, even if your balance stays the same. If your rate rises, your payment rises. You can move your money to a different bank if the rate becomes uncompetitive, but you'll owe taxes on any interest you've already earned in that tax year.

Tax reporting for interest earned

Interest you earn is taxable income. If you earn $10 or more in interest during a calendar year, the bank sends you a Form 1099-INT by January 31 of the following year. You report this amount on your tax return. If you earn less than $10, the bank may not send a form, but you still owe tax on the interest.

The tax you owe depends on your overall income and tax bracket. Interest is taxed as ordinary income, not at a lower capital gains rate. If you have multiple savings accounts at different banks, each bank sends its own 1099-INT, and you add all the interest together on your return.

Frequently Asked Questions

Does interest compound on interest I've already earned?

Yes. When the bank deposits interest into your account, that interest becomes part of your balance and earns interest in the next period. This is called compounding. The more often the bank compounds, the more interest you earn on your interest, though the difference is usually small over short periods.

Can a bank lower my interest rate without telling me?

Yes. Banks can change rates on savings accounts without advance notice unless your account agreement says otherwise. Most banks post rate changes on their website or in your online account. You can check your current rate anytime by logging in or calling the bank.

What happens to my interest if I close my account mid-month?

You keep any interest already deposited into your account. Interest that has not yet been calculated and deposited is usually forfeited. Check with your bank about their exact policy, because some banks calculate interest through the close date and some do not.

Is interest paid the same way at all banks?

The basic process is the same—banks calculate a percentage of your balance and deposit it—but the rate, compounding frequency, and payment schedule vary widely. High-yield savings accounts at online banks often pay much higher rates than traditional banks, sometimes 4% to 5% APY compared to 0.01% at a large national bank.

Do I have to do anything to earn interest?

No. Interest accrues automatically as long as your account is open and has a balance. You do not need to take any action. Some accounts have minimum balance requirements, and interest may stop accruing if your balance falls below that minimum.