The Education Ministry's problem- plagued Novopay system will be the subject of an independent review next year.
The Australian-contracted pay system has seen teachers underpaid, overpaid and not paid at all since its introduction in August, and the project will now be investigated by outside experts in early 2013.
Grilled by MPs at the education and science committee financial review meeting yesterday, Secretary of Education Lesley Longstone said the Novopay rollout would have been "completely and totally different" if done again.
Talent2's Novopay was the most complex payroll system in Australasia. The complexity was magnified when paired with the 10,000 combinations of conditions and allowances in staff contracts, she said.
"We did recognise that it was a very complex pay system at the outset, but we obviously didn't allow for that complexity in terms of time it took to develop the system . . . If I were to do it again, I would probably do it completely and totally different."
Ms Longstone added that she was very confident that, in time, the system would fulfil its promises.
When the payment mechanism was tested, it was found to be "actually very accurate", but there were problems within other parts of the software.
"The system we know is paying a vast majority of staff correctly. However, it is not universally the case.
"I have assured schools and their staff that both the ministry and Talent2 are working extremely hard to put those issues right."
She refused to say what penalties Talent2 would face for not satisfying the terms of its contract, because it was commercial in confidence.
She promised compensation for any financial disadvantage directly caused by Novopay errors, and was not ruling out calls for more general compensation. But at this stage the focus was on getting the system right.
Associate Education Minister Craig Foss welcomed the review, calling the payroll transition issues "unacceptable".
The review would be comprehensive, capturing future milestones like end-of- year  and start-of-year teacher payments for 2013.
Labour's associate education spokesman, Chris Hipkins, claimed National Party committee members had voted against the opposition's request for a select committee inquiry two weeks ago.
"A select committee inquiry could have got to the bottom of the matter in an open and transparent way. What is National trying to hide?"
- The Dominion Post