Interest is money the bank pays you for letting them hold your money

When you deposit money into a savings account, the bank lends that money to other customers through mortgages, car loans, and business loans. In exchange for the use of your money, the bank pays you interest — a percentage of your balance that gets added to your account on a schedule set by the bank. The interest rate varies by bank and by economic conditions, and it changes over time.

The amount you earn depends on three things: how much money you have in the account, what interest rate the bank is offering, and how often the bank compounds the interest (adds it back into your balance so you earn interest on the interest). A $10,000 balance earning 4.5% annual interest will grow differently depending on whether the bank compounds daily, monthly, or yearly.

Key Takeaways

  • Interest rates on savings accounts change based on what the Federal Reserve does with its benchmark rate, so your rate may go up or down over time.
  • The difference between a 0.01% rate and a 4.5% rate on a $10,000 balance is roughly $450 per year, so shopping for rates before opening an account matters.
  • Compounding frequency — daily, monthly, or yearly — affects how much total interest you earn, with daily compounding producing slightly more than monthly or yearly.
  • Interest is taxable income, and the bank will send you a 1099-INT form at tax time if you earned $10 or more in interest during the year.

How the interest rate gets set and why it changes

Banks do not choose their savings rates in a vacuum. The Federal Reserve sets a benchmark interest rate range that influences what banks pay on savings and charge on loans. When the Fed raises its rate, banks typically raise savings rates within weeks or months. When the Fed lowers its rate, savings rates usually fall as well, sometimes more slowly.

The rate you see advertised today may not be the rate you earn six months from now. Banks can change the rate on a savings account at any time, and they are required to notify you before the change takes effect. Online banks and credit unions often offer higher rates than large national banks because they have lower overhead costs and compete more aggressively for deposits.

The difference between simple and compound interest

Simple interest means the bank calculates interest only on your original deposit. If you put $10,000 in an account earning 4% simple interest, you earn $400 in the first year, $400 in the second year, and so on. Your balance grows in a straight line.

Compound interest means the bank adds interest to your balance, and then calculates the next interest payment on the larger balance. If your $10,000 earns 4% compounded annually, you earn $400 in year one. In year two, the bank calculates 4% on $10,400, earning you $416. The difference grows over time. Most savings accounts compound daily, which means interest is calculated and added to your balance every single day, making the growth slightly faster than monthly or yearly compounding.

The math looks small in the short term but adds up. On a $10,000 balance earning 4.5% annually, daily compounding produces roughly $4.61 more per year than yearly compounding. Over ten years, the difference is closer to $50. The real difference comes from comparing banks: the difference between a 0.01% rate and a 4.5% rate on the same $10,000 is about $450 per year.

How often interest gets paid into your account

Even though most banks compound interest daily, they do not deposit that interest into your account every day. The deposit schedule varies: some banks pay interest monthly, some quarterly, and some annually. You can find the payment schedule in the account disclosure document, which the bank must provide before you open the account.

The compounding frequency and the payment frequency are separate things. A bank might compound interest daily but pay it out monthly. This means interest is calculated on a growing balance every day, but you only see the money hit your account once a month. Either way, you earn the same total amount — the payment schedule just determines when you see it.

What happens to interest when you withdraw money

If you withdraw money partway through a compounding period, the bank calculates interest on the average balance or the lowest balance during that period, depending on the bank's rules. Some banks use the "average daily balance" method, which adds up your balance at the end of each day and divides by the number of days. Others use the "lowest balance" method, which pays interest only on the smallest amount you held during the period.

This matters if you make large withdrawals. If you keep $10,000 in the account for 29 days and withdraw it all on day 30, a bank using the lowest balance method might pay you interest on $0 for that month, even though you held the money for most of the period. Check your account disclosure to see which method your bank uses.

Interest income and taxes

Interest earned in a savings account is taxable income. The bank reports it to the IRS and sends you a 1099-INT form at the end of the year if you earned $10 or more in interest. You report this income on your tax return, and you pay income tax on it at your regular tax rate.

This is one reason high-yield savings accounts matter: if you earn $450 in interest instead of $5, you pay tax on $450 instead of $5. The tax is the same percentage, but the amount owed is much larger. Some people move money to savings accounts only when they have a specific goal in mind, to avoid spreading small interest earnings across multiple accounts and multiple tax forms.

How to compare interest rates between banks

The most useful number to compare is the Annual Percentage Yield (APY), which shows the total interest you earn in a year including the effect of compounding. APY is always higher than the stated interest rate because it accounts for compound interest. Banks are required to display APY prominently in their account disclosures and advertisements.

When comparing two banks, look at the APY, not the interest rate alone. A bank advertising 4.50% APY will earn you more than one advertising 4.45% APY, even if the difference seems small. Over a year on a $50,000 balance, that 0.05% difference is $25. Over five years, it is $125. Online banks, credit unions, and some regional banks typically offer higher APYs than large national banks.

Frequently Asked Questions

Can my interest rate go down after I open the account?

Yes. Banks can lower the interest rate on savings accounts at any time and must notify you before the change takes effect. The rate you earn today is not may provide for the life of the account. If rates drop, you can move your money to another bank, but you will earn less interest everywhere.

What is the difference between APR and APY?

APR (Annual Percentage Rate) is the interest rate without compounding. APY (Annual Percentage Yield) includes the effect of compounding. APY is always equal to or higher than APR. For savings accounts, always compare APY to APY, because that is the actual amount you will earn.

Do I have to pay taxes on interest I earned but have not withdrawn yet?

Yes. You owe income tax on interest in the year it is earned, even if it is still sitting in your account and has not been withdrawn. The bank reports it to the IRS on the 1099-INT form, and you report it on your tax return.

Is there a maximum amount of interest I can earn before my account gets closed?

No. Banks do not close accounts because you earn too much interest. However, if you earn a very large amount of interest, the bank may ask you to verify your identity or the source of the funds, as part of anti-money-laundering procedures.

What happens to my interest if the bank fails?

The FDIC (Federal Deposit Insurance Corporation) protects deposits up to $250,000 per account holder per bank. This protection covers both your principal and any interest earned. If the bank fails, the FDIC pays you the full amount, including accrued interest.