Banks pay you interest as a percentage of your balance, calculated daily or monthly, and added to your account on a schedule set by the bank
When you keep money in a savings account, the bank uses that money to lend to other customers. In exchange, the bank pays you interest — a small percentage of your balance. The amount you earn depends on three things: how much money you have in the account, what interest rate the bank offers, and how often the bank compounds the interest (adds earned interest back into your balance so you earn interest on that interest too).
The interest rate varies widely. A savings account at a large national bank might pay 0.01% per year, while an online bank might pay 4% or higher. The difference matters: on a $10,000 balance, 0.01% earns $1 per year, while 4% earns $400 per year. Banks set their own rates based on how much they need deposits and what the Federal Reserve's interest rates are doing.
You do not have to do anything to earn interest. Once you open the account and deposit money, the bank calculates and deposits interest automatically on whatever schedule it uses — usually monthly, but sometimes daily or quarterly.
Key Takeaways
- Interest is money the bank pays you for letting them use your deposits, expressed as a yearly percentage rate of your balance.
- The interest rate varies by bank and account type; online banks typically offer higher rates than large national banks.
- Banks calculate interest daily or monthly and add it to your account on their own schedule, usually once a month.
- Compound interest means you earn interest on the interest already added to your account, which grows your balance faster over time.
- Your interest earnings are taxable income and the bank will report them to the IRS on a 1099-INT form if you earn $10 or more in a year.
How the interest rate is set and what it means
Banks publish an Annual Percentage Yield (APY), which is the total interest you will earn in one year if you leave your money untouched. This is the number to compare between banks. A 4% APY means that on a $1,000 balance, you will earn $40 in a year (before taxes). A 0.01% APY on the same $1,000 means you earn $0.10 in a year.
The APY is not fixed forever. Banks change their rates frequently, sometimes weekly. When the Federal Reserve raises or lowers its benchmark interest rate, banks usually follow within days or weeks. If you open an account at 4% APY, the bank can lower that rate to 2% next month, and you have no say in it. Some banks lower rates faster than they raise them, so it pays to shop around if your rate drops significantly.
The APY already includes the effect of compounding, so you do not have to calculate that yourself. The bank's published APY is the real number to use when comparing accounts.
How banks calculate and add interest to your account
Most banks calculate interest daily. They take your account balance at the end of each day, divide the APY by 365, and add that day's interest to a running total. At the end of the month (or quarter, depending on the bank), they deposit the total interest into your account in one lump sum.
Some banks use a different method called the average daily balance. They add up your balance at the end of each day in the month, divide by the number of days, and calculate interest on that average. This method slightly favors you if your balance fluctuates — a large deposit late in the month counts as much as money you had all month.
A few banks still calculate interest monthly or quarterly instead of daily. This matters if you deposit money mid-month: with daily calculation, you earn interest on that deposit for the rest of the month; with monthly calculation, you might not earn anything until the next month. Always check the bank's disclosure document to see when they calculate.
What compound interest means and why it matters over time
Compound interest is interest earned on interest. Here is how it works: in month one, you earn interest on your original balance. In month two, you earn interest on your original balance plus the interest from month one. In month three, you earn interest on all of that. The longer your money sits, the more this effect adds up.
On a $10,000 balance at 4% APY compounded monthly, you earn about $408 in the first year, not $400. The extra $8 is interest on the interest. In year two, you earn about $424 because you are starting with a higher balance. By year ten, you have earned over $4,800 total, not $4,000. The difference grows the longer you leave the money alone.
The APY already includes compounding in its calculation, so you do not have to do math to figure out how much you will earn. The bank's published APY is the real number.
Why interest rates differ between banks and account types
Online banks typically offer higher APY than brick-and-mortar banks because they have lower overhead costs — no physical branches, fewer employees, cheaper rent. They pass some of that savings to depositors as higher interest rates. A large national bank might offer 0.01% while an online bank offers 4% on the same type of account.
Different account types within the same bank also pay different rates. A regular savings account might pay 0.01%, while a money market account at the same bank pays 0.05%, and a certificate of deposit (CD) pays 4.5%. The bank pays more on CDs because you agree to lock your money away for a set time — three months, one year, five years. The longer the lock-in period, the higher the rate.
Some banks offer promotional rates for new customers — 5% APY for the first three months, then it drops to 0.5%. Read the fine print to see when the promotional rate ends and what the regular rate will be.
How to find your interest earnings and report them on taxes
Log into your online banking portal or call the bank to see your interest earnings. Most banks show interest deposits as a separate line item in your transaction history. You can also request a statement that breaks down interest by month.
If you earn $10 or more in interest during a calendar year, the bank must send you a 1099-INT form by January 31 of the following year. This form reports your interest income to the IRS. You are required to report this income on your tax return, even if the bank does not send the form (though they will if you earned $10 or more).
Interest income is taxed as ordinary income at your regular tax rate. If you earned $500 in interest and you are in the 22% tax bracket, you owe about $110 in federal tax on that interest. Some states also tax interest income. This is one reason high-yield savings accounts matter: earning 4% instead of 0.01% means you have more money left after taxes.
What happens to interest if you withdraw money before the end of the month
If your bank calculates interest daily and deposits it monthly, you earn interest on money you withdraw before the deposit date. If you have $5,000 on day one, withdraw $2,000 on day fifteen, and have $3,000 for the rest of the month, the bank calculates interest on the average or on each day's balance — not just on the $3,000 you had at the end.
With a CD, the rules are different. If you withdraw money before the CD matures, you pay a early withdrawal penalty, which is usually three to six months of interest. If you have a one-year CD at 4.5% APY and you withdraw after six months, you might lose $225 in interest (six months of the $450 you would have earned). The penalty is deducted from your principal, so you get back less than you put in.
Regular savings accounts have no withdrawal penalty, so you can take money out anytime without losing interest you have already earned.
Frequently Asked Questions
Can I lose money if the interest rate drops?
No. Interest is money the bank adds to your account; it never subtracts. If the rate drops from 4% to 2%, you simply earn less interest going forward. Your original balance stays the same. The only way to lose money is if you withdraw it yourself or if the bank fails (though the FDIC insures up to $250,000 per account).
How often should I move my money to a higher-paying bank?
If your current bank drops its rate significantly below what other banks offer, moving makes sense. The effort of opening a new account and transferring money takes a few hours. If you have $50,000 and your bank pays 0.01% while competitors pay 4%, you are giving up about $2,000 per year. Moving is worth it. For smaller balances, the difference is smaller, but it still adds up over time.
Does interest get added if I do not check my account?
Yes. Interest is calculated and added automatically whether you log in or not. You do not have to do anything. The bank tracks your balance and deposits interest on its schedule regardless of whether you watch it happen.
What if I have multiple savings accounts at the same bank?
Each account earns interest separately based on its own balance and the rate for that account type. If you have a regular savings account at 0.01% and a money market account at 0.05%, the money market account earns more interest. The FDIC insurance limit of $250,000 applies per account type per bank, so having multiple accounts gives you more coverage.
Is the interest I earn the same every month?
No. Because interest is calculated on your balance, the amount changes if your balance changes. A month when you deposit $5,000 will earn more interest than a month when you withdraw $2,000. Also, if the bank changes its APY, your interest earnings change starting the next month.