ATO staff are having their performance measured against the amount that taxpayers pay back, something their union says is “unfair and unreasonable”.

The performance benchmark is based on payment plans that ATO staff make with people owing unpaid taxes.

The Australian Services Union says the ATO’s debt unit workers do not have any control over the payments after the plans are made, and so should not be judged on what happens.

The ATO says the measure is a good way to monitor the success of payment plans arranged by tax officials.

Other indicators include staff performance as reported by supervisors, and complaints made by taxpayers owing money to the government.

“This helps the performance of our staff to be measured in a tailored way and gives them a greater understanding of their contribution,” the Tax Office said.

ASU official Jeff Lapidos says tax officials should not be assessed on plans that can fail for reasons beyond their control, especially given that they cannot monitor the payments later.

“I can guarantee you that in the area of debt, there are 10,000 reasons,” he said.

“You're assessing people's individual performance according to something they've got no control over.

“You can only assess staff performance according to what they are asked to do.”