How credit card interest is charged

Credit card interest is worked out on your balance every single day and then charged to your account once a month, when your statement is produced¹. The amount of interest you could pay on any credit card borrowing is worked out as a percentage of the money borrowed¹. That single mechanic drives everything else on this page: why paying in full by the due date costs you nothing on purchases, why leaving even part of the balance unpaid starts interest running on the whole lot, and why a cash machine withdrawal behaves completely differently from a shop purchase.

The headline numbers are worth knowing before the detail. APRs vary very widely across borrowing, and on some credit cards and store cards they run to 25% or more². If you pay off the whole balance owed on the card by the due date, you will not be charged interest on your purchases³. Around 18 million people in the UK have credit card debt⁴, and paying the balance off in full can save you money in interest and charges.

Interest is worked out daily and charged monthly

Credit card interest is calculated daily and charged to your credit card statement when it is produced each month¹. Each day, the card provider works out interest as a percentage of what you owe that day. Those daily amounts are then totalled up and appear as a single interest charge on your monthly statement.

Halifax gives a worked example of how small the daily amounts can look, and how they add up. On a £1,000 balance, from the date of a purchase to the date a minimum payment is taken, the daily interest came to 54.79p in total, calculated using the Simple Annual Rate¹. Fifty-four pence feels trivial; repeated every month on a balance that is not shrinking, it stops being trivial. On a debt of £1,000 at an interest rate of 20%, you could owe £200 in interest after a year⁴.

The practical consequence of daily calculation is that when you pay matters. Interest is a percentage of the money borrowed¹, so every day a balance sits unpaid, another slice of interest accrues on it. Paying mid-month rather than waiting for the due date reduces the number of days the balance is charged for. The statement date, not the calendar month, is what sets the cycle: the interest you see on a statement covers the days since the previous one.

Paying in full each month means no interest on purchases

This is the rule that makes a credit card free to use for many people. If you pay off the whole amount owed on the card by the due date, you will not be charged interest on your purchases³. Citizens Advice states the same in plain terms: if you pay off the total amount by the due date, you will not be charged interest⁸. Provided you pay the bill in full and on time each month, you will not be charged interest⁹.

Most credit cards offer an interest-free period on what you have bought if you pay off your bill in full². This is the gap between buying something and the payment due date, and it exists only for people who clear the whole balance. It is not a grace period on borrowing: it is a reward for not borrowing beyond the statement cycle.

The rule has conditions worth checking on your own card. Halifax, for example, states you will not be charged interest on card purchases if you pay your full main balance, not including any introductory or promotional balances, plus any instalment plan payments, or at least your minimum payment if higher, and did the same the previous statement period¹. In other words, the interest-free treatment of this month's purchases depends on having cleared last month's balance too. Someone who pays in full for the first time after carrying a debt may still see interest on their next statement.

The other condition is that "in full" means the whole balance, not most of it. If you do not pay off the full amount every month on a credit card, you will be charged interest on the whole lot, not just the unpaid amount¹⁰. That surprises people more than any other card rule: paying £90 of a £100 bill does not limit the interest to the £10 left over. The interest-free period page explains how the days are counted, and paying a credit card bill covers the ways to pay.

Interest on interest: how compounding adds up

Once interest has been charged, it becomes part of the balance, and the next day's interest is worked out on the bigger figure. More interest is added as the balance gets bigger¹¹. This is compounding: interest charged on interest already charged.

StepChange illustrates the effect with simple numbers. If you owe £1,000 and have an interest rate of 20%, you could also owe £200 in interest after a year⁴. At 10%, borrowing £1,000 adds an extra £100 in interest in a year¹². Those examples assume the balance is not being paid down; in reality, minimum payments chip away at the debt while interest adds to it, and the two pull in opposite directions. The smaller the payment, the more the interest side wins.

Compounding is also why the order of events matters when a bill is not paid. Interest is charged on the amount outstanding if it is not paid off⁸, and if you do not pay back all that you owe when payment is due, you may be charged interest¹⁰. Each month the cycle repeats on a slightly larger balance, so the same percentage rate produces a slightly larger cash charge than the month before. Over years rather than months, this is what turns a manageable balance into a long-term one: minimum payments are set low enough that clearing a debt at that pace can take a very long time, and the persistent debt rules exist precisely because of it.

The counterweight is that compounding works in reverse too. Every pound paid above the minimum reduces the balance immediately, and with it every day's interest from that point on. Paying off your credit card in full can save you money in interest and charges¹¹.

Different rates for purchases, cash withdrawals and 0% offers

A single card can carry several different interest rates at once, depending on what the borrowing is for. StepChange sets out the three main ones: a purchase rate, when you use your card to buy things; a balance transfer rate, when you move what you owe on one card to another; and a cash transaction rate, when you use your credit card to take money out of a cash machine or get cashback at a till⁴.

Cash is the expensive one. The interest rate for cash advances is usually higher than the interest rate for purchases³, and interest is added to your account straight away, even if you pay off the balance by the due date⁵. There is no interest-free period on cash at all: cash transactions will always charge interest¹². On top of the interest, you may be charged a cash handling fee of around 2% of the amount you withdraw⁵. Which? lists the full price of a cash withdrawal as a withdrawal fee, a higher APR, no interest-free period, and a record on your credit report¹³. Using a card abroad follows the same logic: you will be charged interest on cash withdrawals straight away¹⁴, and paying for foreign currency by credit card is typically treated as a cash advance, with a fee, a higher APR and no interest-free period even if the bill is repaid in full and on time¹³. The cash withdrawals page covers this in detail.

Balance transfers are often the cheap one, for a while. Many balance transfer deals offer 0% interest on the amount you move³. Some cards offer 0% interest deals for a limited period, but there may be a charge for transferring a balance¹⁵. That charge is real: the average balance transfer fee for cards with the longest interest-free periods was 2.97% in February 2023 and had risen to 3.38% by 2024⁶. Moving the debt to a card with low or 0% interest could help you pay off the debt faster¹¹, because while the promotional rate lasts, payments reduce the debt itself rather than servicing interest. When the offer ends the standard rate returns, which the 0% period ending page explains, and missing a payment on a 0% deal can end the offer early.

Purchases sit in between. They get the interest-free period when the bill is paid in full, and the purchase rate when it is not. When you owe money at more than one rate, the card provider applies payments in a set order: the most expensive debt on your credit card will always be paid off first⁵. That sounds helpful but has a catch, since a 0% balance transfer is usually the cheapest debt on the card, so payments clear it last while any purchase debt keeps accruing interest. The balance transfer fees and balance transfer pages cover the mechanics.

What APR tells you, and what it leaves out

APR stands for annual percentage rate. It shows you how much it costs to borrow money over a year, including interest and fees¹⁶. nidirect lists what it takes into account: the total amount of interest you will pay, any additional charges such as a monthly fee for taking out the card, and when and how often you must pay the interest¹⁰. Because it bundles these together, APR is generally higher than the quoted interest rate and shows the true cost of the credit. Lenders have to tell you what the APR is before you sign an agreement¹⁷.

APR is a standard way to compare the cost of loans, and generally a lower APR means a lower cost of borrowing¹⁸. But on credit cards specifically, it has limits:

• It reflects purchases only. The representative example APR you see in credit card adverts reflects the interest charged on purchases, as opposed to cash advances or balance transfers². A card advertised at one rate can charge a much higher one for cash.
• It assumes a fixed pattern of borrowing. The APR of a given product is calculated by assuming that the credit limit is drawn down in full on the first day of the agreement and repaid in 12 equal monthly instalments, with no further transactions¹⁹. Card APRs also use an assumed level of borrowing of £1,200². Almost nobody borrows exactly like that.
• It leaves out penalty charges. The APR does not take into account charges you might have to pay, like a charge for missing your monthly repayment¹⁰.

The representative APR has a legal meaning too: it must be an APR at or below which at least 51% of consumers entering into agreements as a result of the advertisement are expected to pay¹⁹. So nearly half of accepted applicants can legitimately be charged more than the advertised rate. The underlying calculation is set in legislation: the annual percentage rate of charge is calculated by means of an equation which equates, on an annual basis, the total present value of drawdowns with the total present value of repayments and payments of charges²⁰. The APR explained page unpacks the representative example in full.

Typical credit card rates: what the official figures show

Official statistics give one cut of the market: the average credit card interest rate was 21.45 in April 2025²¹. Advertised rates on individual deals vary widely around that average, because providers price their cards differently and the figures measure different things: an average across cards in issue versus the rates on selected new deals.

The direction of travel over time is stark. An FCA review of the credit card market literature, published in 2015, recorded that interest rate charges for credit card debts are usually as high as 15%²². A decade later, typical advertised rates are far above that. Card rates are set by providers and can change: providers can raise the rate on an existing card, with rules about notice and your right to object, which the rate and terms changes and rejecting a rate rise pages cover.

Not everyone with a card is paying interest at all. UK Finance's Household Finance Review for the second quarter of 2024 found the proportion of card debt that is interest-bearing remained just under 50 per cent, a record low since at least 1995²³. In other words, slightly more than half of outstanding card debt is held by people who clear their balance and pay nothing. Around 18 million people in the UK have credit card debt⁴, and the difference between the interest-bearing half and the non-interest-bearing half is mostly the rule in the second section of this page: paying in full, or not.

Missed payments: charges, defaults and court action

Miss a payment and the costs arrive from two directions. Extra charges are added if you miss payments¹¹, and interest is charged on the amount outstanding if it is not paid off⁸. If you do not pay your credit card bill, the company will add on interest each month⁷.

There are rules about how harsh the charges can be. Charges of more than £12 for missing a credit card repayment may be seen as unfair⁵. StepChange lists practices that could be classed as unfair: increasing the rate of interest because you have missed payments; continuing to add interest and charges if you are in financial difficulties; adding charges for actions the creditor has not done; and adding charges which are more than the actual cost to the creditor²⁴. For comparison, high-cost short-term credit such as payday loans is subject to a hard cap, where interest on default charges must not exceed 0.8% of the amount of the charge calculated per day from the date the charge is payable until the date it is paid²². Credit cards are not subject to that cap, but the fairness rules above apply.

If the debt stays unpaid, the consequences escalate. It can affect your credit rating and your debt can be passed on to a debt collection agency²⁵. Court action can follow, and the paperwork has a different name depending on where you live: CCJs (County Court judgments) in England and Wales, Decrees in Scotland, and Civil bills in Northern Ireland⁴.

Two things credit card debt is not:

• It is not a priority debt. Credit card debts are known as non-priority debts, but this does not mean they are not important²⁵. Non-priority debts include credit cards, bank loans, overdrafts and payday loans²⁶. Credit debts are usually a lower priority than debts such as council tax because they cannot be enforced by evicting you from your home, sending you to prison or disconnecting an essential service²⁷.
• It is not a prison matter. You cannot go to prison for simply not paying a credit card debt⁴. Prison is a possibility in rare cases for non-payment of criminal fines, and in England for council tax arrears²⁸, but not for card debt²⁹.

One nuance on priority: if you have an interest-free overdraft with the same bank as a credit card, you could treat such debts as priorities so that you keep the overdraft, because if the bank starts charging interest your overdraft could increase very quickly²⁷. The general rule stands, though: when money is short, what debts to pay first is a question with a clear answer, and free debt advice can help you answer it. The missed payments and court action pages cover the process in detail.

Cutting the interest you pay and where to get help

The levers for paying less interest are few and simple. The first thing to do is stop using the credit card you want to pay off: this means the amount you owe stops growing, making it quicker to repay¹¹. Paying off your credit card in full can save you money in interest and charges¹¹. Where you cannot pay in full, paying more than the minimum each month shortens the life of the debt, because every extra pound reduces the balance the daily interest is worked out on¹. The ways to clear card debt sooner page sets out the options.

A balance transfer can cut the interest rate itself. Many balance transfer deals offer 0% interest on the amount you move³, and moving the debt to a card with low or 0% interest could help you pay off the debt faster¹¹. Weigh the transfer fee, an average of 3.38% on the longest 0% deals in 2024⁶, against the interest you would otherwise pay. Remember the payment order rule: the most expensive debt on your card will always be paid off first⁵, so a transfer works best when new spending on the card stops.

If you are in genuine difficulty, you have rights. Creditors can be asked to freeze interest and charges, and StepChange sets out what counts as unfair practice, including continuing to add interest and charges if you are in financial difficulties²⁴. Free, independent help is available:

• StepChange offers free debt advice online and by phone, including on credit card debt specifically⁴.
• Citizens Advice covers the costs and charges of credit cards across England, Scotland, Wales and Northern Ireland, with nation-specific pages⁵.
• MoneyHelper, the free government-backed service, covers card use and safe shopping online⁹.

For Scotland and Northern Ireland there are dedicated guides to credit card debt in Scotland and credit card debt in Northern Ireland, since court processes and some debt options differ. The main debt section explains the full range of solutions, from informal repayment plans to formal ones, and where each is available.