District Health Boards could owe as much as $1.1 billion to current and former staff in incorrect annual leave payments, and that amount continues to grow.
The DHBs' non-compliance with the Holidays Act was first reported by the Office of the Auditor General five years ago.
RNZ reported on the issue in 2019, which stated that DHBs were still unable to say how of their workers are owed money.
In the recently released 2019/2020 audit, it found money owed to current and former staff goes back more than 10 years in some cases.
"Progressing the payment of the money owed needs to be a high priority."
The Office of the Auditor General noted funding in this year's Budget to the Ministry of Health to help co-ordinate the work needed to determine how much is owed.
"It is important that the health sector reforms do not slow progress and that DHBs work together and with the Ministry of Health to resolve outstanding issues and begin making payments to current and former staff," it said.
The audit reported the aggregate DHB deficit was $1.049b, with only one DHB reporting a surplus and two DHBs reporting a result better than budget.
"Unbudgeted costs affected these results, in particular the provisions for Holidays Act liabilities, which increased by $386.5 million in 2019/20," it said.