A BNZ spokesperson said the bank's systems were now back up and running.
"We can confirm this issue is now resolved and all online and mobile banking services and card payments are available," he said.
"We apologise to our customers for the inconvenience caused."
An update on the bank's Facebook page said "our systems are now operational".
"Customers can now access online banking channels and complete transactions using their BNZ cards," the bank said.
"Our branches will remain closed for the remainder of the day to allow branch staff to assist contact centre colleagues in serving customers on the phone."
"Thank you for your patience."
In an earlier update on the Facebook page from 1.13pm, it said the bank's team is "working hard to implement a fix to the system issues we've been experiencing today".
"While we don't have an ETA to share now we will continue to provide status updates here," it said.
"In the meantime, customers who have had their card declined while using PayWave can try inserting their card into the terminal."
"Unfortunately this is not a solution for 100 per cent of transactions but should prove effective for a large proportion of declined transactions. Credit cards are not impacted by these issues and are working as usual."
Bank customers posted close to 2000 messages below the Facebook update.
"Was just left standing completely embarrassed at a check out, lunch already eaten, card not working and unable to access app or internet banking," the Facebook user said.
"Another lady kindly offered to pay for my bill but this is less than ideal!! Please sort it ASAP."
Another mum said she needs to go out and do her weekly grocery shopping soon.
"I have no options to get back into town for another week! If I don't go soon my kids miss out on food for a week."
Another user said it was not good enough.
"Away on holiday with family with no access to funds," they said.
