ANZ's directors, including former prime minister Sir John Key, could face criminal and civil penalties if they are found to have made false or misleading statements to the Reserve Bank.
The central bank said on Monday that it had requested two reports from ANZ New Zealand, to provide assurance it was operating in a prudent manner.
The first report will cover ANZ New Zealand's compliance with the Reserve Bank's current and historic capital adequacy requirements.
The second report will assess the effectiveness of ANZ New Zealand's director's attestation and assurance framework, focussing on internal governance, risk management and internal controls.
The directors assess whether the bank is complying with the conditions of its regulations through its attestation process.
But the Reserve Bank has since found that they were inaccurately calculating the level of risk capital required as part of those conditions, and censured the bank in May.
The Reserve Bank requires banks to maintain a minimum amount of operational risk capital, which is determined relative to the risk of each bank's business.
According to the Reserve Bank, it "encouraged" ANZ to review its attestation process. When the bank conducted the review, it discovered the issue and alerted the Reserve Bank.
DAVID WALKER/STUFF
Sir John Key has been under pressure in his role as chairman of ANZ.
It could be bad news for the directors if they are found to have filed incorrect information to the regulator.
The Reserve Bank Act allows for bank directors to face criminal and civil penalties if the information in a disclosure statement is found to be false or misleading.
An individual can be jailed for up to 18 months or fined $200,000.
But banking expert Claire Matthews, of Massey University, said it was unlikely the harshest penalties would be applied.
"I would expect one of the findings of the review to be the level of culpability of the directors. I think it unlikely the maximum penalties would be applied, particularly the possibility of imprisonment. I would expect the maximum penalties to apply when the misinformation has been deliberate.
"To date the indication has been that the ANZ misinformation is inadvertent and careless at worst, so any penalties would likely be at the lower end of the scale."
Some commentators have suggested that board embarrassment over the Reserve Bank censure was one reason for chief executive David Hisco's departure.
Former BNZ chairman Kerry McDonald said Key should stand down over the incident.
