The law was amended to introduce simple interest of 8 per cent on legal aid debt from six months, with interest first charged from May this year.
The Ministry of Justice sent letters to 47,000 people with outstanding debt in late 2013, outlining the changes and asking them to set up a repayment plan. That led to 11,205 applying for their debt to be written off last year, 10,306 of whom were successful.
There were 814 successful applications in 2013, and 776 in 2012.
Labour says the figures show that the threshold for free legal aid is too tough. Justice spokeswoman Jacinda Ardern said people are put through the stress of taking on debt they cannot handle.
"The ministry is accepting that there are people who are receiving legal aid, and are being told that they need to pay, who are then later in a financial situation where they are unable to.
"It looks like, not only could we remove a significant amount of stress, improve access to justice, we could also remove a whole lot of unnecessary administration."
Criminal Bar Association president Tony Bouchier said the size of legal aid debt was potentially embarrassing to the Government. "And one way that they can get rid of that embarrassment is by writing off debt."
The Ministry of Justice said working out the value of last year's debt write-offs would take time and would need to be treated as an Official Information Act request.
In announcing the letter drop in August 2013, the ministry said the average debt was $1750. If applied to the number of write-offs last year, more than $18 million would have been forgiven.
Legal aid debt can be wiped when it would cause serious hardship, when it would be just and equitable, or when enforcement costs are likely to exceed the amount owed. About 80 per cent of recipients don't incur legal aid debt because they fall under an income threshold, but others are required to repay some of the grant.
A spokeswoman for Associate Justice Minister Simon Bridges referred questions to the ministry.
Michelle McCreadie, general manager of Legal Aid Services, said it was expected that the letters would result in an increase in debt write-offs.
This did not demonstrate that the initial assessment was wrong, and there were no plans to review criteria used. "Writing off debt is not about our collections efforts. It's about a person's ability to repay their debt against the specified criteria."
