On most savings accounts, APY accrues daily and is credited to your balance monthly. The annual percentage yield is an annual figure, but the interest behind it builds every day your money sits in the account, and the bank posts the accumulated earnings once a month, usually on your statement date. On a $10,000 balance at 4% APY, that comes out to roughly $32 to $33 in the first month, growing slightly each month as the new interest starts earning its own interest.
Accrual and Crediting Are Two Different Events
Interest accrues the moment your money is sitting in the account earning a return. Crediting is when the bank actually adds those earnings to your visible balance. For most savings accounts the two happen on different schedules: accrual runs daily, crediting happens once a month, typically aligned with your statement cycle. In the weeks between crediting dates, the interest you’ve earned exists on the bank’s books but hasn’t been posted yet, so your balance won’t reflect it.
Federal rules require interest to accrue on the full principal each day, using either the daily balance method or the average daily balance method.1eCFR. 12 CFR 1030.7 – Payment of Interest Nothing in the regulation forces a particular compounding frequency, so banks vary. Most online high-yield accounts compound daily; some traditional banks compound monthly or quarterly. Either way, the monthly credit is the moment the earnings become spendable balance.
Accrual also continues right up until you take your money out. Federal law requires interest to accrue until the day you withdraw funds.1eCFR. 12 CFR 1030.7 – Payment of Interest If you deposit $5,000 on the 15th of the month, you earn interest only for the days that money was actually in the account. A deposit made late in a cycle doesn’t retroactively earn interest for the full month.
How to Estimate Your Monthly Interest From APY
The quickest estimate is to multiply your balance by the APY and divide by 12. On $10,000 at 4% APY, that’s $10,000 × 0.04 ÷ 12, or about $33.33. That’s close enough for budgeting.
The precise monthly number is slightly smaller in the first month and slightly larger by the end of the year, because each month’s earnings are a fraction bigger than the last. The exact monthly rate derived from APY is (1 + APY)^(1/12) − 1. At 4% APY, that works out to about 0.3274% per month, which on $10,000 produces $32.74 in the first month. By the twelfth month, the balance has grown enough that the monthly credit is a bit higher, and the total for the year lands at exactly $400.
The official APY formula in Regulation DD works in the other direction. It starts from actual interest earned and days in the term, then annualizes: APY = 100 × [(1 + Interest/Principal)^(365/Days in term) − 1].2CFPB. Appendix A to Part 1030 – Annual Percentage Yield Calculation That’s how the bank arrives at the APY it advertises. You don’t need it to check your statement, but it explains why two accounts with the same nominal rate but different compounding schedules show slightly different APYs.
When Interest Starts Accruing on New Deposits
Cash deposits begin earning interest the same day. Check deposits follow a different timeline under Regulation CC, which governs fund availability. A bank must start accruing interest no later than the business day after it receives credit for the deposited check.3eCFR. 12 CFR Part 229 – Availability of Funds and Collection of Checks (Regulation CC) In practice, expect a one- to two-day lag between depositing a check and having it earn interest, depending on how quickly the paying bank settles. That lag can shrink your first monthly credit if you funded the account partway through the cycle.
Does Compounding Frequency Change the Monthly Number
Barely, on a savings account. On a $10,000 deposit at a 4% nominal rate, daily compounding produces an APY of about 4.08%, yielding roughly $408 over the year. Monthly compounding at the same nominal rate produces an APY of about 4.07%, yielding roughly $407. That’s less than a dollar’s difference across a full year, and a fraction of a cent per month. Compounding frequency matters more on multi-year CDs or at higher rates. For a standard savings account, the compounding interval isn’t worth losing sleep over.
What does move the number is the nominal rate that sits behind the APY. Banks are required to disclose both when you open an account, and the APY captures the full effect of compounding over 365 days.4eCFR. 12 CFR 1030.4 – Account Disclosures On a daily-compounding account with a 3.93% nominal rate, the APY works out to about 4.01%. The gap is small on savings, wider on products with less frequent compounding or higher rates.
Closing the Account Before Interest Posts
Because accrued interest doesn’t hit your balance until the monthly credit, timing matters when you’re moving money. If you close a savings account before the monthly crediting date, you may lose the interest that has accrued but hasn’t yet been posted. Banks are allowed to include this forfeiture in their deposit contracts, but they must disclose it upfront when you open the account.5CFPB. 12 CFR 1030.4 – Account Disclosures Withdrawing all funds before the crediting date can be treated as closing the account, which triggers the forfeiture. If you’re planning to transfer your balance elsewhere, waiting a day or two past the credit date can save you the current month’s earnings.
Your Monthly Interest Can Change Without Warning
The APY on most savings and money market accounts is variable, which means the number driving your monthly credit isn’t fixed. Banks do not have to give you advance notice before lowering a variable rate.6eCFR. 12 CFR 1030.5 – Subsequent Disclosures The 30-day advance notice requirement that applies to other adverse account changes specifically exempts variable-rate adjustments. Your rate can drop today with no notice, and next month’s credit will reflect the change for whichever days of the cycle the new rate was in effect.
At account opening, the bank must disclose that the rate and APY may change, how the rate is determined, and how often it can change.4eCFR. 12 CFR 1030.4 – Account Disclosures After that, monitoring rate changes is on you. If a specific monthly dollar amount matters to your plan, a fixed-rate product like a CD is the only way to lock it in, and CDs come with their own trade-off in the form of an early withdrawal penalty. On a variable savings account, the monthly credit is a moving target.
One last thing worth checking against your monthly credit: fees and balance tiers. A $10 monthly maintenance fee on an account earning $15 a month in interest cuts your take by two-thirds, and some accounts advertise their top APY only up to a threshold, dropping to a lower rate on balances above it. The APY disclosed for your specific tier is the one that drives your credit, not the headline number in the ad.