ONE News has obtained a leaked copy of an official report showing the flawed Novopay system could take up to two years to fix.
The brief was given to Steven Joyce, the minister now in charge of sorting out the widespread and ongoing problems.
Freemans Bay School in Auckland sees errors every pay cycle, and principal Sandra Jenkins has been dealing with a staff member who is owed $1700.
"She had to go to the bank and request that the mortgage payment not go out, she had to make credit arrangements so that she could pay her mortgage so that she could buy food," Jenkins said.
The minister was told problems like these could take two years to fix if nothing changes.
ONE News has obtained a copy of the briefing from the Ministry of Education to Steven Joyce, which was written last week and was not meant to be released yet.
The document says: "If we do nothing to change the users' experience, we can expect it to take 18 to 24 months before the Novopay system is delivering at the level that we expected."
Joyce said there would be changes because that time frame "would be unacceptable". But he couldn't give a timeframe for when the issues would be fixed.
"I don't have a particular period of time and I'm not going to try and venture one today. But it is certainly unacceptable what's going on now," he said.
He previously said anybody who gives a definite timeframe "is actually dreaming".
Green Party co-leader Metiria Turei said Joyce has been dishonest with New Zealanders by not warning them of the potential two-year timeframe before the system will work.
"He needs to be more accurate and more clear with families and schools because they are the ones that bear the brunt of this serious problem," she said.
The document also reveals the Ministry has a backlog of over 1100 enquiries made by school staff, and it is employing more payroll experts to sort things out.
Novopay has its own call centre, but the wait to speak to someone has often been "unacceptably long", and staff frequently provide incorrect information.
A chain of correspondence between supplier Talent2 and the Ministry of Education was released yesterday, revealing the testing and roll-out of the system was so beset with problems it was delayed three times - and almost scrapped.
The documents also revealed three Cabinet ministers signed off on the project, knowing there were 147 defects. But it is unclear if officials revealed the true scale of problems to ministers. A ministerial inquiry begins next week to determine who is to blame.
Joyce yesterday conceded he did not have a "high level of confidence" that the system could be fixed. His admission came just a day after he said dumping Novopay was not the "simple solution".
Next week's pay round is expected to be chaotic, with a new secondary school teachers' collective agreement coming into play.
"I think it would be unfair to say I'm massively confident, but I've certainly got to make the best of the situation we are in," Joyce said.
- With Fairfax