NHS Tayside is investigating after some staff were overpaid outstanding holiday pay.
The foul-up follows changes ordered by the Scottish Government in how holiday pay for staff is calculated.
NHS Tayside made these assessments and an interim payment of arrears was to be included in December 2015 salaries.
But the health board has now admitted there were issues in how the money was paid out and are trying to establish if some workers need to pay money back.
It is understood that the issue affected Site Support Services staff within NHS Tayside, which includes relief porters who work flexible shifts.
Some are thought to have received money they were not supposed to have and they are worried about the sums of cash they may have to pay out following an expensive Christmas period.
NHS Tayside’s director of HR, George Doherty, said: “In response to previous Scottish Government instruction issued to all health boards on changes to how pay for staff during leave should be calculated, NHS Tayside Board agreed that an interim payment of any arrears should be included in December 2015 salaries.”
He added: “Staff affected by possible errors in some payments were notified immediately.
“Any payments made in error will be reclaimed in line with normal board policy.”