More than $3 million of ACC money was lost to fraud last year and culprits increasingly include widowed women ripping off the system.
Nearly 100 people have been prosecuted for fraud since 2007 and figures released to the Herald under the Official Information Act reveal the total savings to the taxpayer from the detection of last year's fraud alone was $37 million.
Although the total amount of fraud in the 2010/11 fiscal year was $3.1 million, the higher figure of $37 million is reached when the impact the fraud would have had on taxpayers if it was not discovered was taken into account.
A growing group of fraudsters is women whose husbands have died as a result of injury - and who wrongly continue to receive payments when they enter into new relationships.
Last month, Georgina Hiromena Timoti, 52, was convicted of defrauding ACC of $109,653 and was sentenced to 10 months' home detention and 150 hours' community work.
The Whakatane woman claimed benefits after her husband died in an accident in 1981.
She entered into a de facto relationship in 1985 but continued to tell ACC she was single and received payments she was not entitled to.
Ms Timoti was also ordered to pay $30,000 in reparation.
ACC's general manager of claims management, Denise Cosgrove, said there were "creative people out there" when it came to trying to rip the system off.
The recent cases of widows being caught receiving payments were some of the "unusual" examples staff had encountered.
"The other ones I've seen recently are around the partners who are really engineering the whole thing and not the injured person, so they're quite interesting as well," she said.
Those instances were balanced against the bulk of cases which primarily were people claiming payments when they were not really injured or continued to work.
Ms Cosgrove said the money lost through fraud was eye-watering.
"The simple thing is we have a zero tolerance towards fraud and that's whether it's coming from claimants, providers, levy payers or staff.
"I guess the big point is that ripping off ACC is actually ripping off all New Zealanders because that impacts on the levies we pay."
She said instead the agency's concern should be on injured people who genuinely need their help, and if wrongdoing wasn't detected it would impact on the levies paid "so it really is a fraud against all New Zealanders".
ACC has a dedicated investigations unit to find fraudsters and as well as using intelligence gained through analysing data, documents and trends they rely on tip-offs from members of the public anonymously ringing in and sending emails.
"They get quite a bit through those avenues," Ms Cosgrove said.
In the year to last October 31 there were five fraud case prosecutions as well as ongoing cases.
Georgina Hiromena Timoti, 52, of Whakatane, was convicted last month of 25 charges under the Crimes Act for offending between 1984 to 2009.
She pleaded guilty and was sentenced to 10 months and one week of home detention, 150 hours of community work and ordered to pay reparation of $30,000.
ACC discovered she had repeatedly misled its staff about her relationship status in order to claim benefit payments intended for the single surviving spouse of a person who died as a result of injury.
Timoti received $109,653 she wasn't entitled to.
Karyn Peta June Blake, 47, of Blockhouse Bay, Auckland, was sentenced to six months' home detention last month for defrauding ACC.
She pleaded guilty to 10 charges under the Crimes Act of claiming benefit payments intended for the single surviving spouse of a person who died as a result of injury.
Blake applied for the benefit after her husband died in an accident in 1990.
Although she subsequently twice entered into a marriage-type relationship, she supplied ACC with numerous declarations stating that she was not in such a relationship.
She received in total $39,460.