Customers who try to overpay on their credit card could find their attempt to clear more of their balance doesn't work, potentially leaving them trapped in a debt spiral.
Thousands of Lloyds TSB, Halifax and Bank of Scotland customers have been left frustrated after being unable to send or receive Faster Payments. In the worst cases, people have been left without their wages, but the banks say they will refund charges.
Halifax and Lloyds TSB customers have reported that they cannot access their cash from ATMs, while online banking isn't working and even debit cards are not working in shops, on one of the biggest party nights of the year.
Many Northern Rock customers have discovered their loans are not protected by the Consumer Credit Act (CCA), despite having documents which say they're covered.
Traders may be misleading consumers by not making it clear they have signed up to regular card payments, or that these can be cancelled, the Office of Fair Trading says.