Kiwibank has apologised to customers after a system outage on Christmas Eve which may have sparked mistaken bank charges. 

About 4.45pm, minutes before many shops closed their doors to last minute shoppers, the bank's system crashed - and for at least one customer the outage lasted 45 minutes. 

An issue with Kiwibank's cards payment system meant some customers were unable to make payments for "approximately 20 minutes", a Kiwibank spokesman said. 

"The issue was quickly resolved and we have apologised for any inconvenience caused." 

One man, who didn't want to be named, was at technology store JB HI-FI, buying his wife some headphones when the outage struck. 

"I walked up to the counter and swiped my card and it came up with 'card not honoured', and I said 'there's money on the card' so I tried a different card and it happened again," he said. 

The Auckland man had half an hour before the store closed at 5.30pm. 

Like many others affected, he quickly rang Kiwibank to find out what the problem was and was on hold half an hour. 

"The guy said all of our credit cards and eftpos cards aren't working at the moment." 

Luckily, the system was up and running again two minutes before JB HI-FI closed, the man who spoke to the Herald said. 

That meant he was able to get his last Christmas present. 

"My back up option was to tell my wife I wanted to buy her a Christmas present but the bank said I had no money." 

He was fortunate he'd finished all his children's presents and was able to get his wife's just in time, the man said. 

Kiwibank customers left in last minute panic on Christmas Eve after system crashes. Photo / File 

"I imagine others might not have been so lucky." 

In a "Securemail" to him from Kiwibank, the bank apologised for the system outage. 

"We understand that it has been extremely upsetting and difficult for our customers. If you have been charged any bank fees as a result of these outages, then please let us know so that we can get them reversed," the email said. 

The customer the Herald spoke to said he had not experienced any unexpected bank fees.