Although most new card customers only take the time to look at the APR, and how long the introductory interest-free period lasts for, there are dozens of other differences between cards – all of which can end up costing you money if you’re not careful.

The most common trick is to only allow you to pay off the lowest interest bearing debt on your card first. For example, if you spend £500 on your card one month, and then another £500 the next, any subsequent payments you make will go towards paying off the most recent transactions first. Meanwhile, the £500 you spent in the first month will continue compounding interest. The only lender not to pull this trick is Nationwide.

Jumping the gun to make a few more pennies

Other cards start charging interest from the moment you make a purchase, rather than the moment the transaction clears on your card (usually three days later). And while some cards allow you an interest free period on every transaction (meaning you’ll pay no interest at all if you pay your balance in full before that day), others do not.

Fairer Deals

The industry is right to say that consumer choice may be reduced if it is forced to standardise its pricing – and some consumers will indeed be worse off. But thousands of customers who are (usually unbeknown to themselves) propping up the lenders’ profits would at least get a fairer deal.

Unfortunately, the majority of those who get caught out, and pay additional charges, are the customers who can least afford it. Meanwhile, the chief beneficiaries of the opaque and complex system are those of us who probably could afford to pay a little more for the convenience of owning a credit card.