Payroll failures at National Australia Bank will cost it $169 million after stiffing thousands of workers for more than a decade.
The financial giant committed to paying $127 million, $34 million in interest and $8 million in superannuation in an enforceable undertaking with the Fair Work Ombudsman.
A $2 million contrition payment has also been imposed, the ombudsman said on Thursday.
The contrition payment is the largest included in an enforceable undertaking ordered by the ombudsman.
Back payments to the 66,000 impacted workers range from less than $5 to more than $87,000, including superannuation and interest, with an average back payment of about $1900.
NAB executive Sarah White said the bank takes it payroll obligations "extremely seriously".
"We sincerely apologise for these unintended errors. We have and will continue to remediate anyone who has been impacted," she said.
But the Financial Services Union lambasted the bank and said it was one of the worst cases of employee underpayment in Australian corporate history.
"Underpayment of wages is theft, pure and simple, and is unacceptable at any employer," the union's national president Wendy Streets said.
"It is hard to believe a big four bank with all its resources would make such a colossal mistake over such a long period of time."
NAB first self-reported underpayments to the ombudsman in late 2019, becoming aware it made significant errors when applying its most recent enterprise agreement.
An internal review found they stretched back to 2012 due to record-keeping mistakes and outdated payroll technology being transferred across systems.
Administrative blunders were discovered such as recording correct time-sheet data, staff not accruing leave correctly and other entitlements under successive enterprise agreements.
Never-before terms in the undertaking include a commitment to comprehensive planning and compliance with any future enterprise agreement.
Fair Work Ombudsman Anna Booth said the bank had committed to fixing its administrative systems.
"NAB's underpayments highlight the serious, long-running problems that can arise when an employer fails to coordinate key business functions to meet their workplace obligations," Ms Booth said.
Payroll expert Brett Cowan warned that some of the country’s biggest employers could be sitting on millions of dollars in payroll mistakes because their systems compound the same error annually.
"It's a business risk, and it belongs on the board's agenda and if a company can't explain how its payroll calculations work, its board should be asking why," he said.
The ombudsman recovered than $450 million in unpaid wages and entitlements for more than 181,000 workers in 2025/26.
The bank, which ranks third in size behind Commonwealth Bank and Westpac, achieved a net profit of $6.14 billion in 2026.
