Martin Lewis has issued an "important" reminder to Britons with credit cards about how a small oversight could still drain their wallet. The MoneySavingExpert.com founder shared the video on his X profile, alerting households to an important quirk of credit card interest rules they should be aware of.

"This is an important warning about the way that credit cards work," the personal finance guru said. "Imagine you've spent £1,000 on the credit card. If you then pay off the £1,000 so you totally clear it, there is no interest in the month."

"But if you were to pay off £999.99, so you're just a penny short, you don't pay interest on a penny for the month, you still pay the interest on the entire £1,000."

Mr Lewis said it's the reason why, for years, his catchphrase has been: "Pay off your credit card IN FULL!", bellowing the two important words.

"The 'IN FULL' is important," he added. "I talk about it when it's a credit card reward, say for getting cashback, or for cheap spending on a credit card abroad.

"Because if you do the IN FULL, you neuter the credit card's ability to charge you interest. If you miss even a penny, it can still charge you a whack."

However, rules are slightly different for withdrawals, Mr Lewis explained this in a recent episode of his BBC podcast.

Interest on the cash you take out starts accruing immediately, with no "grace period" before you repay it.

It's worth noting that many banks and building societies will charge you additional fees to take out cash using a credit card, as well as charging interest.

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