Thousands of Halifax customers are being given lump sum payments after missing out on the monthly rewards they were due.
Until last summer, holders of the Halifax Clarity credit card who also had a current account with the bank were entitled to a £5 cashback every month if they spent at least £300.
But a processing error at the bank meant that many customers didn't get the cash they were due, with some missing payments dating back to 2011. A spokesperson tells MoneySavingExpert that as many as 1.5% of Clarity cardholders may be affected.
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Halifax is now paying back affected customers, with a small amount of compensation as well as the missed £5 payments. The average amount they're getting is £86, although some customers have received more than £100. Most have been contacted automatically, and the bank is crediting payments to their accounts.
"Between September 2011 and July 2016 there were some occasions when we didn't pay you a reward payment when we should have," the letter from Halifax reads.
"I'm sorry that this happened that it's taken us longer to resolve than it should have. To put this right and make sure you haven't lost out, we're paying you the money we owe and some extra interest."
However, it says, customers who no longer have a Clarity card are taking a little longer to track down - so it may be worth getting in touch with the company yourself.
It's worth noting that the Halifax Clarity card stopped paying the £5 cashback last summer. But there are several others that offer rewards, including American Express and TSB.
Meanwhile Sainsbury's Bank, M&S Bank, Debenhams Bank and Tesco Bank, for example, pay out store points to their customers; others offer air miles or points that can be spent in certain retailers.
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However, these schemes are only good value if you manage your money carefully.
"The interest rates on reward and points credit cards are not normally particularly competitive," warns Moneysupermarket.com.
"These cards are therefore only really suited to people who can afford to clear their balance in full every month. If you allow debts to build up, you will almost certainly pay more in interest than you will get back in rewards."
And, of course, it's only worth going for one of these cards if you're actually going to use the reward. There's little point collecting air miles if you never fly; or points for retailers that you never use.