Kiwibank is poised to replace its core banking platform, originally built to support building societies, with new system from global giant SAP.
The change is tipped to cost up to $100 million, but the bank isn't commenting ahead of an announcement, expected later this week.
At the beginning of last year, CEO of New Zealand Government-owned Kiwibank, Paul Brock, said the bank was focused on its IT infrastructure to cope with its growth and regulatory requirements.
"It's too early to tell when or if we may make any changes to our core banking system," he said.
Two years earlier the bank opted to stay with its existing system, developed by Ultradata.
Now, it appears, the change is on and a contract with German software giant SAP is expected to be inked.
The chairman of Kiwibank's parent company NZ Post, Sir Michael Cullen, told a parliamentary select committee last week a supplier would be announced soon. News website Stuff is reporting industry sources tipping SAP as the chosen provider.
Kiwibank, which has 850,000 customers, was launched in 2002.