Westpac says its card services are working again after a systems issue yesterday.
Its website, online banking, card services and contact centre went down before 2pm on Monday.
The bank posted on social media saying it was experiencing a network issue affecting access to its website and Westpac One online banking.
Westpac NZ general manager commercial, corporate and institutional banking Simon Power said staff worked through the night to fix the problem.
He said Some New Zealand Superannuation payments and beneficiary payments that were due to go out on Monday night were delayed by the issues, but should now be in people's accounts.
The delays also extended to some customers of other banks, whose banks receive the government payments via Westpac, Power said.
"We know this is already a stressful time for many New Zealanders and we apologise for the inconvenience this has caused."