A savings account can calculate interest every day while adding it to your balance only once a month. Those statements describe different events: the calculation builds an amount owed; the credit date is when the bank posts that amount. Looking for a separate daily transaction can therefore make a correctly operating account appear to be doing nothing.
For a real example of the distinction, NatWest’s Digital Regular Saver information describes daily calculation and payment on the first business day of the month. That is an example of one product’s terms, not a universal timetable or a recommendation to open the account.
Follow the balance through the month
Consider an invented account with a constant annual gross rate of 3.65%, a 365-day calculation basis and a balance of 1,000 currency units. A simple daily calculation would produce 0.10 per day. Thirty days at that unchanged balance would produce 3.00 before any rounding, tax or other product rules. The example explains the timing; it is not a current rate quotation.
If a withdrawal reduces the eligible balance halfway through the period, the later days need their own calculation. Multiplying the final balance by the whole month’s days would miss the money that was present earlier. A rate change during the month creates a similar need to split the calculation.
Keep three entries beside your statement: the date a deposit became eligible, the applicable rate period and the scheduled credit date. Check the account’s own definition of balance and its treatment of weekends, closure and rounding. Do not assume another account at the same bank uses identical rules.
If the posted figure still looks wrong, ask the bank for the calculation period and eligible daily balances. Giving it those specific dates is more useful than comparing the payment with an annual headline rate divided by twelve. Monthly payments need not be identical when months, balances or applicable rates differ.