If you have an interest-free deal on your credit card, listen up! Do you know when your deal’s due to end?

You might expect your credit card provider to drop you a line to let you when the offer ends – that is, when you’ll start paying interest on your balance. But, shockingly, that’s not always the case.

We’ve discovered that a number of credit card providers don’t actually notify customers before their 0% interest free offer expires.

We did a mystery shopping exercise and found that interest free periods can range from nine to 27 months, and credit card providers are keeping schtum about when the offer period runs out. Customers are then are rolled on to APR rates that can go up to as much as 52%.

If you have a 0% interest deal on new purchases, only a few of the providers may actively tell you when this is due to end. Some providers like AA, MBNA and Sainsbury’s will print the end date of the 0% deal on each statement, and TSB and Tesco do make some efforts to tell you when it will end.

But the worst four offenders are: Bank of Scotland, Santander, SAGA and Yorkshire & Clydesdale Bank. These four were found not to display offer end dates on monthly credit card statements during our mystery shopping exercise.

M&S Bank, Barclaycard and Lloyds don’t put the expiry date on statements, but they say that the last statement before the change will tell you how much interest will be charged on your next bill, based on the current balance.

While there are no rules for the card companies about this at the moment, we don’t think this is fair. And nor do customers.

86 per cent of credit card customers/holders in the UK say they’d like to hear when they will soon be paying a higher rate of interest. And over two thirds of people say that receiving that notification would make them shop around and switch credit cards. And that’s probably a key contributing factor for why credit card brands aren’t as transparent as they could be.

So we’re is calling for all credit card providers to pro-actively contact customers 30 days before their offer period expires. In the meantime, check when your deal ends so you don’t get caught out.

And don’t forget, you can check any time for the best credit card deals to see if you can save money. It’s fast and simple – just click here.