Christmas will be a trying time for thousands of Bay education professionals plagued by the faulty Novopay system.
Bay of Plenty principals are at breaking point with the $26 million payroll system, with one saying those affected would be left in an "extremely vulnerable position" leading up to and during the Christmas break.
Robert Hyndman, president of the Western Bay Principals' Association, said the situation at present, which mostly affected school support staff on wages but also some full-time teachers, was unacceptable.
The Brookfield School principal said paysheets were being botched, with people's hours worked and their payment received not matching up.
"For example, if someone has worked seven hours at a certain rate you should be able to work out how much they should get paid, but it's simple maths gone wrong and it's causing huge problems," Mr Hyndman said.
"Add it to the fact that the report sheets are extremely difficult to read, where even I can't even understand where some of this money is coming from."
Overpayment was a big problem in the Western Bay with a number of affected staff giving the money back to their school for "safe keeping" during the Christmas break, he said.
"Overpayment is just as difficult to correct as underpayment.
"I would say this has caused an increased amount of stress and workload in this last week, not just for me, but for other principals and school staff all around the Bay. I'm aware of one teacher at another school being so wound up by all this that she burst into tears," Mr Hyndman said.
Education professionals are set to receive one more payment before Christmas but Mr Hyndman wasn't confident it would go smoothly.
"We're now facing the next big challenge, with teachers getting their holiday pay right up until January 28 ... but it could all go horribly wrong so I'm not holding my breath," he said.
At Tauranga's Kaka St Special School, 13 staff were affected in the last payment.
Principal Barrie Wickens said one staff member was set to be overpaid by $4000, but after complaining to Novopay, the amount was decreased to $400.
"It has been reduced but it's still not correct. This is just another classic example of Novopay getting it wrong," Mr Wickens said.
The school would financially support those who were underpaid, he said.
"This has taken a huge toll on affected staff and caused a lot of stress and worry ... and has put some people into financial stress at a time that's already stressful."
Nearly every school in the Western Bay has been affected by pay inaccuracies since the implementation of the Novopay system in August.
New Zealand Education Institute president Ian Leckie said Novopay problems were endemic throughout the country.
"The Ministry of Education has unleashed a catastrophe and we don't believe this is something that can be sorted this side of Christmas," Mr Leckie said.