Interest accrues daily but posts on a schedule that depends on your bank
Most banks calculate interest on your savings account balance every single day, but they add that interest to your account on a schedule — usually monthly, sometimes quarterly. The daily calculation is called daily compounding. The day they actually deposit the interest is called the posting date. These two things are separate, and the difference matters for how much money you end up with.
Your bank takes your account balance at the end of each day, applies the annual interest rate to it, and divides by 365 (or 360, depending on the bank's method). That tiny daily amount gets added to an invisible running total. Then, on the posting date — usually the last day of the month — the bank moves all that accumulated interest into your account at once. From that point forward, you earn interest on the interest, which is called compounding.
The frequency of posting matters because it affects how much you earn over time. A bank that posts monthly will give you more total interest than one that posts quarterly, even if both calculate daily. The more often interest posts, the sooner you start earning interest on that interest.
Key Takeaways
- Interest is calculated every day based on your current balance, but it is not added to your account until the posting date, which is usually the last day of the month.
- Monthly posting is the most common schedule; quarterly and annual posting are less common and result in lower total earnings over time.
- The annual percentage yield (APY) you see advertised already accounts for how often interest compounds, so you can compare accounts fairly.
- Your balance grows faster if you deposit money early in the month, because that money earns interest for more days before the posting date.
- Some online banks post interest daily or weekly, which is rare but means you start earning on your interest sooner.
Why banks calculate daily but post monthly
Daily calculation gives you a more accurate picture of what you owe interest on. If you deposit $1,000 on the 15th and withdraw $500 on the 20th, the bank needs to know that you earned interest on $1,000 for five days and $500 for the remaining days of the month. A daily calculation method handles this automatically.
Monthly posting is standard because it simplifies accounting for both the bank and you. Your statement shows one interest deposit per month, not dozens of tiny daily deposits. It also reduces the number of transactions the bank has to process. Some banks use quarterly or annual posting to reduce costs even further, but this is becoming less common as online banking has made frequent posting cheaper to manage.
How compounding works when interest posts
On the day interest posts, your balance jumps by the amount earned that month. The next day, the bank begins calculating interest on this new, higher balance. This is compounding in action.
Example: You have $10,000 in an account earning 4.50% APY, posted monthly. In month one, you earn roughly $37.50 (10,000 × 0.045 ÷ 12). On the posting date, your balance becomes $10,037.50. In month two, you earn interest on $10,037.50, not just the original $10,000. Over a year, this compounds to more than simple interest would give you. The APY figure already includes this compounding effect, so the 4.50% is what you actually earn, not a starting point.
What posting frequency means for your total earnings
The difference between monthly and quarterly posting is small in the short term but adds up over years. A $10,000 balance at 4.50% APY posted monthly earns about $450 per year. Posted quarterly, the same account earns roughly $448 per year — a difference of $2 annually. Over ten years, the gap widens to around $20 to $30.
The reason is timing. With monthly posting, you start earning interest on your interest eleven times per year. With quarterly posting, only three times. The more frequent the posting, the more often you earn on your earnings.
Daily posting is rare but does exist at some online banks. It means interest hits your account every day instead of waiting until month-end. This gives you the maximum possible compounding, though the practical difference from monthly posting is usually less than $5 per year on a typical balance.
How to find your bank's posting schedule
Your account agreement or the bank's website will state the posting frequency. Look for language like "interest is credited monthly" or "compounded daily, posted monthly." If you cannot find it online, call the bank's customer service line and ask directly. The answer should take one minute.
Some banks show the posting date on your monthly statement. If your statement always shows interest on the last day of the month, that is your posting date. If it varies, the bank may be posting on a different schedule or adjusting for weekends and holidays.
When timing of deposits affects how much you earn
Money deposited early in the month earns interest for more days before the posting date. Money deposited late in the month earns interest for fewer days. This is why depositing on the first of the month rather than the 28th results in slightly more earnings by year-end.
The difference is small — a few cents on most balances — but it compounds. If you have the choice, depositing early maximizes the number of days your money earns interest before the first posting date. After that, the posting schedule matters more than the timing of individual deposits.
Comparing accounts using APY instead of interest rate
Banks advertise an annual percentage yield (APY), not just an interest rate. The APY already includes the effect of how often interest compounds and posts. This means you can compare two accounts fairly without doing math yourself.
If Bank A offers 4.50% APY and Bank B offers 4.50% APY, you will earn the same amount over a year, regardless of whether one posts monthly and the other posts quarterly. The APY is the real number. The interest rate and posting frequency are the mechanics behind it.
If you see an interest rate without an APY, ask the bank for the APY. The rate alone does not tell you what you will actually earn.
Frequently Asked Questions
Does my money earn interest every day even if it posts monthly?
Yes. The bank calculates interest every day based on your balance, but it does not add it to your account until the posting date. You are earning interest daily; you just do not see it in your balance until it posts, usually at month-end.
What happens to interest if I withdraw money before the posting date?
You lose the interest that would have been earned on the withdrawn amount for the remaining days of the month. If you withdraw $500 on the 20th of a 30-day month, you do not earn interest on that $500 for days 21 through 30. The interest already earned on it through day 20 still posts.
Can I move money between accounts to earn more interest?
Moving money between your own accounts at the same bank does not increase total interest earned, because the bank calculates interest on your combined balance. Moving money to a different bank with a higher APY does increase earnings, but only if the new account's APY is genuinely higher and you keep the money there long enough to offset any fees.
Why do some banks post interest weekly instead of monthly?
Weekly posting means you start earning interest on your interest more often, which compounds faster. It is rare because it costs banks more to process frequent transactions. Online banks are more likely to offer it because their lower overhead makes frequent posting affordable.
Does the posting date change if it falls on a weekend?
Usually yes. If the posting date is the last day of the month and that day is a Saturday or Sunday, most banks post on the last business day before it. Some post on the first business day after. Your account agreement or statement will show which method your bank uses.