The board of ANZ bank knew about NZ chief executive David Hisco's personal expenses which were paid with company money for the past three months, NZ chairman Sir John Key said.
Hisco's personal use of chauffeur-driven cars and wine storage costs using the bank's money have cost him his $3 million-a-year job.
The chief executive's expenses stretched back nine years and amounted to "tens of thousands of dollars" around the ballpark of $50,000.
Shayne Elliot, chief executive of Australia's ANZ bank, undertook a review of expenses within the bank's leadership and anomalies were found, Key said.
"[Elliot] looked through the bulk of his executives - they came up with and couldn't quite work it out," he told Heather du Plessis-Allan on Newstalk ZB.
"Shane said 'we can see some anomaly here but we can't quite work it out', and so they went away and did an investigation that took quite some time.
"There was a discussion shared with myself and David, don't know exactly how long ago but a number of weeks ago."
Asked why it took so long for Hisco to lose his job, Key said because of ill-health being delicate employment matters, the announcement was delayed.
Key said the issue does not involve how much money was spent but rather how that spend was characterised in the records.
The former Prime Minister earlier told the Herald a lack of transparency over the expenses resulted in them being mischaracterised in ANZ's books.
"We have got to be consistent with the standards we set, from the freshly minted teller to the CEO," Key said.
"He believed that he had authority for this. He had an explanation for why it was recorded in the way it was.
"I don't believe it meets the standard that David would set under normal circumstances."
Once identified, the issue was handed to the ANZ NZ board - that Key chairs - to make a call.
Key said Hisco's departure was mutually agreed between the CEO and the bank. Hisco was, however, not present at the press conference.
Key furthermore said that there weren't any systemic problems in senior leadership and that anomalies weren't detected in other executive's accounts.
ANZ executive Antonia Watson will be stepping into the role vacated by Hisco as acting CEO.
"We are fortunate to have an experienced executive in Antonia Watson to step in while we conduct a search for a replacement," said Key.
"Antonia's extensive banking career has her well-placed to help ANZ manage through this transition."