The rate advertised for a savings account is only one part of the calculation. The amount actually earned also depends on the balance method, compounding, when transactions post and the account’s disclosed terms.
The interest rate and APY answer different questions
The interest rate is the rate the bank applies to an eligible balance. The annual percentage yield, or APY, expresses the return over a year and reflects the effect of compounding under standardized assumptions.
APY makes deposit products easier to compare, but it is not a promise that every account will earn that exact dollar return. Actual earnings change when balances, rates, fees or the amount of time funds remain in the account change.
The balance method determines the amount that earns
Consumer deposit accounts generally use a daily balance method or an average daily balance method. One applies a daily periodic rate to the principal in the account each day; the other applies a periodic rate to the average of the applicable daily balances.
An account may also have a minimum balance, rate tiers or other conditions. The disclosure should explain the method and which balance is used, so two accounts with the same headline rate can still produce different results for a customer whose balance moves during the month.
Interest can accrue before it is credited
Accrued interest is interest the account has earned under its terms but that the bank has not yet posted to the account. A bank may calculate accruals daily while crediting the accumulated amount monthly, quarterly or on another disclosed schedule.
Once interest is credited, it becomes part of the recorded account balance. Whether uncredited interest is paid when an account closes, and how early withdrawals affect a time deposit, depend on the account agreement and applicable requirements.
Compounding lets credited interest earn interest
When credited interest remains in the account, later calculations may include it in the principal that earns interest. More frequent compounding can increase the effective annual return, although the difference may be modest at lower balances or rates.
Compounding frequency and crediting frequency are related but not identical ideas. The product disclosure provides the rules needed to understand how the bank moves from a stated rate to the interest shown on the statement.
A simple estimate still needs assumptions
Multiplying a steady balance by an APY can provide a useful annual estimate. It becomes less accurate when the balance changes, the rate is variable, qualification conditions are not met or fees reduce the account’s value.
The clearest way to review actual earnings is to compare the disclosed method with transaction dates, daily or average balances, the interest credited and the annual percentage yield earned shown for the statement period when required.
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