Interest is credited on a schedule, and the schedule changes the total

What follows is an argument about how interest is credited, and about where the received version of it stops being true.

Accrual and crediting are different events

Interest usually accrues daily on the balance, but it is only added to the account on a defined date, which may be monthly, annually or at maturity. Until it is credited, accrued interest is not part of the balance and therefore is not itself earning anything. That gap is why two accounts quoting an identical rate can pay different amounts across the same year.

The effect is small on modest balances and short periods, and it becomes visible on larger balances held for years. It is a mechanical consequence of compounding frequency rather than a difference in generosity between providers.

Why a standardised figure exists

Most regulated markets require providers to quote a standardised annual equivalent figure that assumes interest is left in the account. The purpose is to allow accounts with different crediting frequencies to be compared using a single number.

For most households, an account paying monthly will show a standardised figure slightly above its simple rate, because the monthly credits compound. The names and precise definitions of these standardised figures differ between countries, which matters when comparing across borders. What does not differ is the principle: compare the standardised figure, not the headline rate, when the crediting frequencies differ.

When the assumption breaks

The standardised figure assumes interest stays in the account, so it overstates the outcome if you take the interest as income. Some accounts pay monthly interest specifically to provide an income stream, and for those savers the simple rate is the relevant number. The same applies where interest is paid away to a different account automatically, which is common on fixed-term products.

Reading which of the two behaviours an account has is more useful than reading the rate, if income is the objective. Providers generally state this in the summary box, and the wording is usually explicit about where interest goes.

Withdrawing before the credit date

On some accounts, closing or withdrawing before the interest is credited forfeits the interest accrued since the last credit. On others, interest is calculated to the date of withdrawal and paid, which is a materially better outcome for the saver. This is a term rather than a rate, so it does not appear in any comparison table and has to be read in the account conditions.

For most households, it matters most on fixed-term and annually crediting accounts, where a year of accrual can be at stake.

Where a withdrawal is planned, timing it after a credit date rather than before is a free improvement.

Timing across a tax year

In countries where savings interest is taxable, the year in which interest is credited usually determines when it is assessed. An annually crediting account can therefore concentrate several years of interest into one assessment if it matures that way. That concentration can interact with allowances and thresholds, which is a reason some savers prefer monthly crediting.

On the balance sheet, the rules on this differ substantially between jurisdictions and change over time, so nothing general can be relied upon. Anyone with sums large enough for this to matter should confirm the position with their tax authority or a qualified adviser.

Assume any product feature can be withdrawn at renewal.

Checking an account in two minutes

The three facts worth extracting are the crediting frequency, where the interest goes and what happens on early withdrawal. All three sit in the account terms rather than the advertisement, and they take a couple of minutes to find. Together they explain most of the difference between what a saver expected and what actually arrived.

Practically, on small balances none of this changes much, and treating it as a decisive factor would be a misallocation of attention. This is general information about how accounts are structured and not a recommendation about any particular product.

The takeaway

Compare the standardised annual figure, then check when interest lands and what happens if you leave before it does.

Write the number down before you decide. It usually decides for you.