What happens to your money when you put it in a savings account

When you deposit money into a savings account, the bank lends most of it out to other customers as mortgages, car loans, and business credit lines. In exchange for letting the bank use your money, they pay you interest — a percentage of your balance, calculated and added to your account on a schedule the bank sets. The interest rate they offer you is almost always lower than the rate they charge borrowers, which is how banks make their profit.

The amount of interest you earn depends on three things: how much money sits in the account, what annual percentage yield (APY) the bank is paying, and how long your money stays there. A bank might advertise a 4.5% APY, but that does not mean you earn 4.5% of your balance every month. It means that if you kept the same balance untouched for a full year, you would earn 4.5% of it by the end of that year.

Banks calculate interest in different ways — some daily, some monthly, some quarterly. The more often they calculate it, the more you earn, because you start earning interest on your interest. This is called compounding. If a bank compounds daily, they divide your APY by 365, calculate that tiny fraction of your balance, add it to your account, and then the next day they calculate interest on the new, slightly larger balance.

Key Takeaways

  • Interest is the payment a bank makes to you for letting them use your money, expressed as an annual percentage yield (APY).
  • The actual interest you earn depends on your balance, the APY rate, how long your money stays in the account, and how often the bank compounds interest.
  • Daily compounding earns you more than monthly or quarterly compounding because you earn interest on your interest.
  • Banks are required to disclose their APY and compounding frequency before you open an account, usually in a document called the Truth in Savings disclosure.
  • Interest rates on savings accounts change over time and vary widely between banks, so the rate you see today may be different in three months.

How the compounding schedule changes what you actually earn

Imagine you have $10,000 in a savings account with a 4% APY. If the bank compounds interest annually, they calculate 4% of $10,000 once a year, which is $400. You end the year with $10,400.

If the same bank compounds daily instead, they divide 4% by 365 days, which is about 0.011% per day. On day one, they calculate 0.011% of $10,000 (about $1.10) and add it to your account. On day two, they calculate 0.011% of $10,001.10 (about $1.10 again, but slightly more because your balance grew). By the end of the year, daily compounding earns you about $408 instead of $400 — an extra $8 on the same rate and balance. The difference grows larger as your balance grows and as time passes.

Most savings accounts compound daily, and many high-yield savings accounts also compound daily. Some money market accounts compound daily. Certificates of deposit (CDs) vary — some compound daily, some monthly. The bank's disclosure document will tell you which schedule they use.

Why interest rates on savings accounts move up and down

Banks do not set savings account rates on their own. They respond to the federal funds rate, which is the interest rate the Federal Reserve sets for banks to lend to each other overnight. When the Fed raises this rate, banks can charge borrowers more for mortgages and loans, so they can afford to pay depositors more to attract savings. When the Fed lowers the rate, banks lower what they pay you.

The relationship is not one-to-one. If the Fed raises its rate by 0.5%, a bank might raise its savings APY by 0.3% or 0.6% or nothing at all, depending on how much money they need to attract and how much competition they face. Banks in competitive markets (usually online banks) tend to raise rates faster and higher than banks with many physical branches, because they cannot rely on convenience to keep customers.

This is why a savings account that paid 0.01% APY in 2021 might pay 4.5% APY in 2024, and why that same account might pay 2% in 2026. The rate you see advertised today is not locked in — it can change at any time, and banks typically notify you by email or through your account portal when they do.

The difference between stated APY and what you actually see in your account

Banks must disclose their APY, but the APY assumes your balance stays the same all year and you make no withdrawals. In real life, you deposit money at different times, withdraw for expenses, and your balance fluctuates. The bank still calculates interest on whatever balance you have on each day they compound, so your actual earnings will be lower than the advertised APY suggests — unless you add money regularly, in which case you earn interest on the new deposits too.

Some accounts have minimum balance requirements. If you must keep $2,500 in the account to earn the advertised rate, and your balance drops to $2,400, the bank might drop your rate to a much lower tier or pay no interest at all. Read the disclosure document to see whether your account has tiers and what happens if you fall below the minimum.

How to find the disclosure document and what to look for

Before you open a savings account, banks are required by federal law to give you a Truth in Savings disclosure (also called a Regulation DD disclosure). This document lists the APY, the compounding frequency, any minimum balance requirement, what happens if you close the account early, and whether the rate can change. Most banks post this online before you open the account; some require you to request it.

When you are comparing accounts, look for three things: the APY (not just the interest rate, which is different), how often interest compounds, and whether there is a minimum balance. If one account offers 4.5% APY compounded daily with no minimum, and another offers 4.5% APY compounded monthly with a $25,000 minimum, the first account will earn you more money and be easier to maintain.

What happens to your interest if you withdraw money before the year ends

Unlike CDs, savings accounts have no penalty for withdrawals. You can take out money whenever you want, and you keep all the interest you have already earned. If you deposit $5,000 on January 1 and withdraw $3,000 on June 15, the bank calculates interest on $5,000 for the first 165 days, then on $2,000 for the remaining 200 days. You earn less interest overall because your average balance was lower, but you do not lose what you already earned.

Some accounts limit how many withdrawals you can make per month without a fee. Federal rules used to cap this at six withdrawals per month, but that rule was suspended in 2020 and has not been reinstated. Individual banks may still have their own limits, so check your account agreement.

How interest rates on savings accounts compare to other places to keep money

Savings accounts are not the only place that pays interest. Money market accounts typically offer slightly higher rates than savings accounts but may require a larger minimum balance. High-yield savings accounts (offered mostly by online banks) often pay more than traditional savings accounts at brick-and-mortar banks. CDs lock your money away for a set term — three months, one year, five years — and usually pay more than savings accounts in exchange for that restriction. Treasury bills and bonds, issued by the U.S. government, currently pay more than most savings accounts but carry different risks and rules.

The tradeoff is usually between how much you earn and how easily you can access your money. A savings account lets you withdraw anytime with no penalty. A CD pays more but charges a penalty if you withdraw early. A Treasury bill is backed by the government but requires a minimum purchase amount and has a maturity date.

Frequently Asked Questions

If I have $10,000 at 4% APY, how much interest will I earn in one month?

Roughly $33, assuming daily compounding and no deposits or withdrawals. The bank divides 4% by 365 days (about 0.011% per day), multiplies that by your balance each day, and compounds the result. The exact amount depends on the number of days in the month and whether the bank uses a 365-day or 360-day year in their calculation.

Can a bank lower my interest rate without warning?

Yes. Banks can change savings account rates at any time without your permission. They must notify you, usually by email or through your account portal, but they do not need your approval. If you disagree with a rate cut, you can move your money to another bank.

Why do online banks pay more interest than big banks?

Online banks have lower overhead costs — no branches, fewer employees, less real estate — so they can afford to pay depositors more to attract savings. They compete on rate rather than convenience. Big banks with many branches rely on customer loyalty and location, so they can pay lower rates and still keep deposits.

Does interest earned on a savings account count as income for taxes?

Yes. Any interest you earn over $10 in a calendar year must be reported to the IRS on your tax return. The bank will send you a 1099-INT form in January showing how much interest you earned the previous year. You report this as taxable income on your federal return.

What is the difference between APY and APR on a savings account?

APY (annual percentage yield) includes the effect of compounding and shows what you actually earn. APR (annual percentage rate) does not include compounding and shows only the base rate. Banks must disclose APY for savings accounts, so that is the number to use when comparing accounts.