Frustrated BNZ customers tonight are again experiencing payment issues after the company suffered its second major outage in just days. 

In a post on social media, BNZ said it's "aware" customers cannot use BNZ credit cards or payWave. 

"Online banking balances and transactions are also not currently showing for credit cards. 

"We're working hard and fast to fix the problem and will let you know as soon as it's resolved. We apologise sincerely for any inconvenience caused by this technical issue." 

Carolyn, from South Waikato, said this was the second time recently that she had been unable to use her BNZ card. 

She was at the checkout in Countdown today buying meat for dinner around 5pm when her card declined. 

She had cash so was able to pay for the food, but she was embarrassed and "stressed out" at being declined. 

"Whether you've got the money or not you still get looked at." 

On Saturday, customers were unable to log in to online banking services, catching out hundreds of customers at supermarkets and other stores. 

That outage was reported at 10.19am and was not resolved until about 3.20pm. 

The BNZ website states the company is "investigating" the current outage. 

Many customers expressed their disappointment on social media. 

"I've had two declined transactions on my debit card and it is incredibly embarrassing and inconvenient. I think you need to do something about it," one person wrote. 

"Why are there so many issues? I thought these were fixed over the weekend," another asked.