Fine dodgers had managed to outrun the government for so long it has been forced to write off $100 million in unpaid debt. But the government is still chasing $774 million from 2.8 million individual debts, a figure which is expected to grow. Like a forgotten block of cheese in the back of the refrigerator, the State Penalties Enforcement Registry debt had been allowed to "grow mould and fester" and a "cleanse" of the books had been necessary, Treasurer Tim Nicholls said. "Much of it was over five years old and in fact some of it was over 10 years old," Mr Nicholls told an estimates hearing on Tuesday. It was quite simply unrecoverable. Mr Nicholls authorised the write-off in 2012-13. The past financial year also had debt lodgements hit a record high, with 1.3 million unpaid fines lodged with SPER, a 40 per cent increase from the year before. Mr Nicholls put the jump down to unpaid failure to vote fines, with both the state and local elections having been held in 2012. The agency collected $242.8 million in debt during 2012-13, which was $34.4 million more than the year before. Mr Nicholls said new information powers had been provided, which better identified debtors, helping with fine recovery. But the agency also shifted focus to target "high-value debtors," who, in some cases, owed more than $50,000 to the government. Mr Nicholls said concentrating on those big fines that had been overdue by more than nine months had netted the government $3.4 million. Mr Nicholls said the government was "making inroads" into the problem of recovering money from fine dodgers, rather than "just wringing our hands and saying it's all too hard." "We have got behind SPER, we have given them some resources, we have improved efficiency and we are starting to recover those funds," he said. But the government is not just relying on its own agency to recover monies owed to it. Four mercantile agencies - Australian Receivables Ltd, Baycorp, Dun & Bradstreet and National Credit Management Ltd - were appointed to take part in a debt recovery trial in October last year. About 50,000 debt files were shared between the agencies, which were ordered to "identify and locate as many debtors as possible." Mr Nicholls said the first part of the trial had been judged a success, and the cost of contracting the outside debt collectors was expected to be exceeded by the amount of debt they recovered. A formal assessment of the trial will be completed later this month.