Widow fraudsters have stolen more than $763,000 from taxpayers by claiming ACC payments for their dead partners despite starting new relationships.
A review by Accident Compensation Corporation investigators found 11 clients had supplied false declarations to receive ongoing payments as the surviving spouses of people who died accidental deaths.
But widows receiving the accidental death entitlements must tell ACC when they start a new de facto relationship or marriage.
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.
Three women were charged and eight others face potential prosecution, according to figures obtained under the Official Information Act. The total amount wrongfully claimed was $763,943.
One woman was jailed for lying about her relationship status.
Sharon Rebecca Andrew was sentenced to 16 months in prison by Judge Duncan Harvey in July. The 51-year-old defrauded ACC of nearly $150,000 and pleaded guilty to 22 charges of dishonestly using a document and three charges of making a false statement.
Ms Andrew began receiving the weekly payments after her de facto partner died in an accident in 1983, but she subsequently entered into a marriage-like relationship with a new partner.
Despite having three children with her new partner and declaring themselves "husband and wife" when buying property together, Ms Andrew kept telling ACC that she wasn't in a marriage-like relationship and continued to claim the payments.
When confronted by investigators, Ms Andrew denied any wrongdoing but admitted to all charges against her when she appeared in court.
ACC claims manager Denise Cosgrove said the prison sentence sent a "strong message that the courts won't tolerate deliberate, calculated ACC fraud".
"ACC collects levies to help people with genuine injury-related needs. Offending such as this therefore amounts to theft from honest, hard-working New Zealanders."
Two other women escaped jail terms.
Karyn Peta June Blake, 47, was sentenced to six months' home detention in December after pleading guilty to 10 charges of making dishonest declarations.
Her husband died in an accident in 1990 but she kept claiming the ACC payments despite entering into marriage-type relationships twice. In total, she received $39,460 of illegal claims.
Georgina Hiromena Timoti, 52, was sentenced to 10 months' home detention and 150 hours of community work for making false statements to receive $109,653. She was also ordered to pay $30,000 reparation for the offending, from 1984 to 2009.
* $763,000 of taxpayers' money.
* Illegal payments for nearly 30 years.
* ACC clawing money back from 11 clients.
* 3 charged, 8 others face potential prosecution.