Beneficiaries who were underpaid by a day's worth of benefit are now getting their money, some receiving hundreds of dollars in back pay.
Work and Income has paid most benefits a day late for almost 20 years and is trying to pass legislation to wipe the debt.
But beneficiaries are claiming back the extra day's pay and, in some cases, getting it.
Benefits are meant to start the same day a stand-down period ends, usually a couple of weeks after someone first applies.
RNZ reported in September that since 1998, the government had been starting payments the day after stand-down.
Since then, advocates have been helping people claim the extra day's pay, sending out hundreds of review forms, which are forwarded on to Work and Income.
Aaron Tily, who lives in Ashburton, has just received $93.
"Quite relieved, because it took quite a bit of time," he said.
"My family was thinking it might have been a bit of a scam, and I was starting to think that as well."
The Facebook group set up to get people claiming the extra day now has more than 4500 members.
Those members have been posting about how much money has arrived in their account, which in some cases amounts to hundreds of dollars.
Beneficiary advocate Kay Brereton said the payouts so far ranged from $40 to $300, depending on how many times people had been on and off the benefit.
"This is what we want to encourage, is people to get off the benefit and have jobs and just use the benefit when they need to, and don't have a job.
"It's these people that have been disadvantaged, and it's these people who are being back paid, so it's fantastic."
RNZ asked the Ministry of Social Development under the Official Information Act how much the government could owe beneficiaries because of the mistake, and how many had filed reviews, but the ministry refused to release the information.
Ms Brereton said more than 500 people had asked for the money back so far, and she expected many more would now the payments had started.
Another advocate, Shelley Hannah-Kingi, said hundreds of thousands of beneficiaries could have been affected.
"Rightfully, these people should have been back-dated, because some of them have missed out on more than one day.
"Some of them, seasonal workers, could be one day for each 18 years." If every eligible person applied, the government could find itself $100m in debt, she said.
But it was also about the principle.
"Because they're owed it under law and it's not ethical to not follow our laws just because people are poor, and we make bad judgments about them. That's not okay."
Minister of Social Development Anne Tolley would not confirm people were being backpaid - saying only that reviews were dealt with on a case by case basis.
In a statement, she said benefits were now issued on the correct day, bringing it in line with the law.
"Having revisited this issue, I directed Work and Income to change its practice so that it technically aligns with the letter of the law and last year's court decision, ahead of an upcoming law change which clarifies the policy intent."
The Green Party had been advocating for the government to backpay the beneficiaries, and MP Jan Logie said it was fantastic to see it happening.
It affected many people, she said.
"Seasonal workers who are likely to have been going on or off the benefit once or twice a year... Educational support workers quite often don't get paid in the holidays in those jobs, so they will go on and off the benefit maybe three times a year."