National Australia Bank will take a $130 million to its earnings in the 2025 financial year after a review found that the bank had underpaid its staff.

Operating expenses in the three months of the 2025 financial year are now expected to be about 4.5 per cent more than fiscal 2024, the bank said on Monday.

NAB spokeswoman Sarah White said paying its staff correctly was “an absolute priority”.

Know the news with the 7NEWS app: Download today

“We are sorry and apologies to our colleagues that this has happened and have commenced remediating those impacted,” she said.

A payroll review carried out in 2019 has cost the bank $250 million, the bank said, adding that the review is “ongoing” and the total costs are not known.

Max Moran, CEO of payroll compliance provider Subi, said NAB’s case highlights the “systemic” problem in Australia and that “it’s not enough to fix mistakes after the fact”.

“$130 million is a big number but the real story is thousands of workers who weren’t paid correctly, “he said.

“The lesson from NAB is clear: manual payroll checks can’t keep up with Award complexity. Without automation and regular audits, businesses will continue to miss obligations.”

NAB is due to announce its full-year results on November 6.