How credit card interest works
You may see an annual rate on your statement but an interest charge every month. That is not a contradiction. The annual figure describes the rate; the provider’s calculation determines how much is added to your account.
An annual rate is not a monthly charge
Do not multiply the balance by the full annual percentage to estimate one month’s interest. For a deliberately simplified example, £1,000 at a 24% simple annual rate would cost about £19.73 over 30 days if the balance stayed unchanged: £1,000 × 0.24 ÷ 365 × 30.
This arithmetic explains the idea; it is not a quotation. It excludes fees and compounding. A simple annual rate is not interchangeable with an effective annual rate or APR.
Why the dates matter
Lloyds explains that it calculates interest daily and adds it to the monthly statement. With this approach, purchases and payments on different days affect the charge.
Different parts of a balance can also have different rates. Purchases, cash transactions and balance transfers may not be priced alike. Check your statement’s breakdown.
When purchases can be interest-free
Many cards offer an interest-free period for purchases if you meet the repayment conditions. Paying in full by the due date matters, but previous statements and other balances may matter too. Check your agreement rather than assuming every payment type is treated alike.
A 0% promotion on a balance transfer is separate. It does not automatically make new shopping interest-free.
Why interest may appear after you paid
If you carried an interest-charging balance, interest may build up between the statement date and the day your payment arrives. It can appear on the following statement, often called residual or trailing interest.
A statement produced on the 1st cannot include the exact interest that will accrue before a payment arrives on the 10th. Check the next statement even if you intend to stop using the card. Ask for an explanation if the charge is unclear.
Which figure belongs in a calculator?
Our calculator uses an effective annual interest rate and converts it to a monthly rate. APR can include standard fees, and a simple annual rate uses a different convention. Those distinctions matter when comparing an estimate with a real bill.
If your statement shows several rates, do not average them by eye. Identify the rate for the balance you are modelling, or ask the provider to explain it. For the exact amount due, use the statement.
Sources & further reading
- Lloyds: credit card interest rates ↗
- MoneyHelper: a simple guide to credit cards ↗
- Lloyds: residual interest ↗
Sources checked on 3 November 2026. Examples are illustrative unless identified as reported figures or a provider’s terms. General information, not personal financial advice.