Interest posts to your account on a schedule set by your bank, usually daily or monthly
When you hold money in a high yield savings account, the bank calculates what you owe based on your balance and the annual percentage yield (APY) they've promised. That calculation happens constantly — most banks do it daily. But the actual deposit of interest into your account follows a separate schedule: some banks post interest daily, some weekly, and most post monthly on a set date.
The timing matters because interest that hasn't posted yet doesn't earn interest itself. If your bank calculates daily but posts monthly, you're earning on the same principal for 30 days before that interest joins your balance and starts generating its own returns. This is why the difference between daily posting and monthly posting can add up over a year, though the effect is usually small for most account balances.
Key Takeaways
- Banks calculate interest daily based on your balance and APY, but post it to your account on their own schedule — daily, weekly, or monthly depending on the bank.
- Interest posted to your account becomes part of your balance and earns interest itself in the next calculation cycle.
- You can see the interest posted in your transaction history, and it will be labeled as "interest paid" or similar language specific to your bank.
- The APY you see advertised already accounts for the effect of compounding, so you don't need to calculate it yourself.
- Interest is reported to the IRS on a Form 1099-INT if you earn $10 or more in a calendar year, and you owe income tax on it.
The daily calculation versus the posting date
Your bank looks at your account balance every single day and calculates how much interest you've earned that day. The formula is straightforward: (balance × APY) ÷ 365. If you have $10,000 and the APY is 4.50%, you earn about $1.23 that day. The bank keeps a running total of these daily calculations.
The posting date is when the bank actually moves that accumulated interest into your account as a deposit. If your bank posts monthly on the 15th, it adds up all the daily interest from the 1st through the 14th and deposits it as a single transaction on the 15th. Starting the 16th, your new, higher balance begins earning interest for the next month. This is compounding — your interest earns interest.
A few banks post daily, meaning the interest calculated on day one is already in your account and earning returns on day two. This compounds more frequently and results in slightly more total interest over time. The difference is real but usually small — on a $10,000 balance at 4.50% APY, daily posting versus monthly posting might add $2 to $3 per year.
How the interest appears in your account
When interest posts, it shows up as a deposit transaction in your account history. The label varies by bank — you might see "Interest Paid," "Interest Deposit," "Monthly Interest," or straightforward "Interest." The amount is always the accumulated interest from the calculation period, never broken down by individual days.
The posted interest when ready becomes part of your available balance. You can withdraw it, transfer it, or leave it to earn more interest. There's no waiting period or hold. Some banks show the interest separately in a line item on your statement; others roll it into your total balance without a separate line. Check your bank's statement format to see how they display it.
If you move money out of the account before interest posts, you don't lose the interest you've already earned — the bank calculates based on the balance on each day, so you keep the interest from the days the money was there. If you withdraw $5,000 on the 10th of the month and interest posts on the 15th, the interest calculation includes the higher balance from the 1st through the 10th and the lower balance from the 11th through the 14th.
Why the advertised APY already includes compounding
The APY (annual percentage yield) you see advertised is not the same as the interest rate. APY includes the effect of compounding — the fact that interest earns interest. A bank might quote you a 4.50% APY, and that number already assumes your interest will be posted and start earning returns.
You don't need to do any math to account for compounding yourself. The APY is the actual return you'll see over a year if you leave the money untouched. If you deposit $10,000 at 4.50% APY and make no other transactions, you'll have $10,450 after one year (before taxes). The bank has already done the compounding math for you.
APY can change at any time. Banks lower it when market rates fall and raise it when rates rise. Your current rate applies only to interest posted going forward — interest already in your account at an old rate stays at that rate. When a bank changes the APY, the new rate applies to the next interest posting cycle.
What happens if you close the account before interest posts
If you close your account on the 10th of the month and your bank posts interest on the 15th, you won't receive that interest. The bank calculates it based on the balance while the account was open, but if the account no longer exists, the interest has nowhere to go. Some banks will mail you a check for accrued but unposted interest; others keep it. Check your bank's policy before closing.
To avoid losing interest, close your account after the posting date, not before. If you know your bank posts on the 15th, wait until the 16th to close. The interest from that month will already be in your account and will transfer with you if you move the balance elsewhere.
Interest and your taxes
The interest your bank posts is taxable income. You owe federal income tax on it at your ordinary income tax rate, and you may owe state income tax depending on where you live. The bank reports this to the IRS on a Form 1099-INT if you earn $10 or more in a calendar year.
You'll receive the 1099-INT by January 31st of the following year. It shows the total interest posted to your account during the previous calendar year. You report this amount on your tax return, and the IRS matches it to what the bank reported. If you earned interest but didn't report it, the IRS will notice the mismatch.
Interest earned in a high yield savings account is treated the same as interest from any other source — there's no special tax treatment. If you're in a high tax bracket, the after-tax return on a 4.50% APY account might be closer to 3% depending on your tax rate.
Frequently Asked Questions
Can I withdraw my interest before it posts?
No. Interest that hasn't posted yet doesn't exist in your account — it's only a calculation the bank is tracking. Once it posts, it becomes a real deposit and you can withdraw it when ready. If you need the money before the posting date, you can withdraw your principal balance, but the unposted interest stays with the bank until the posting date arrives.
What if my bank changes the APY after I deposit money?
The new rate applies only to interest calculated after the change takes effect. Interest already posted at the old rate stays at that rate. Interest calculated on future balances uses the new rate. If your bank lowers the APY, you'll see the effect in your next interest posting — the deposit will be smaller than the previous month.
Do I earn interest on interest that's already posted?
Yes. Once interest posts to your account, it becomes part of your balance and earns interest in the next calculation cycle. This is compounding. If you earn $50 in interest one month and it posts, that $50 is now part of your balance and will earn interest the next month along with your original principal.
Why does my interest amount change month to month?
The amount of interest you earn depends on your balance during each day of the calculation period. If you deposit a large sum mid-month, the interest posted that month will be higher than the previous month because your average balance was higher. If you withdraw money, the next month's interest will be lower. Seasonal changes in your balance create natural variation in monthly interest deposits.
Is interest posted on weekends or holidays?
Most banks post interest on the same calendar date regardless of the day of the week. If your bank posts on the 15th and the 15th falls on a Saturday, interest typically posts that Saturday. Some banks post on business days only, so if the 15th is a holiday, they post on the next business day. Check your bank's specific policy in their account agreement or by calling customer service.