ACC fraudsters have ripped off taxpayers by more than $10 million in the past four years.
Figures released to the Herald reveal 64 people have been convicted for ACC fraud in that period, including "injured" clients who keep working and medical practitioners who bill for too much treatment.
The total amount ranges from $1.8 million to $3.5 million each year, although ACC says the scams would have cost taxpayers much more if the fraudsters had not been caught.
Stopping the frauds saved a further $131 million, according to figures released under the Official Information Act.
In the most recent financial year, ACC uncovered $3.5 million of false claims. Using actuarial methodology, ACC calculated the true cost would have been $35.9 million if the fraud was undetected and ran its expected course.
Many fraudsters are clients who keep working while receiving weekly compensation for lost earnings, lie about an accident, injury or their incapacity, or make false declarations or alter documents.
Among those convicted were widows who stole more than $763,000 by claiming ACC payments for their dead partners despite starting new relationships.
In some cases, the illegal payments went on for nearly 30 years and one woman was paid nearly $150,000.
The long-running rorts were discovered when the ACC started a nationwide review dating back to the 1980s.
In a separate case, a married couple were convicted in October for each making false claims.
Carl Adam Rutherford and Haley Ann Rutherford were each sentenced to 100 hours of community work and ordered to pay reparation of $8188 and $7683 respectively.
The Southland dairy farmers began receiving weekly compensation from ACC after separate accidents in 2002.
Both went on to work in different jobs while receiving weekly compensation, despite signing declarations stating that they were not in work or receiving income that could affect their entitlement to the compensation they were receiving.
ACC's general manager of claims management, Denise Cosgrove, says this was a disappointing example of deliberate offending, as the couple worked for various different employers while continuing to claim ACC's help.
"Most New Zealanders feel a sense of repugnance at this type of offending," Denise Cosgrove said.
"ACC exists to help people with genuine injury-related needs, and it's disappointing to see some people use it deceitfully for their own financial gain."
ACC also investigates medical practitioners who claim for treatment or services not provided, or claim extra time with clients, provide treatment when not needed or forge documents.
Levy payers who misrepresent their levy class to minimise levy rates, or understate or do not declare earnings to minimise levy rates are also investigated.