Hundreds of health workers across Northern Ireland are being affected by a fresh problem linked to the glitch-hit payroll system, it has emerged.
After months of staff being underpaid following errors with tax and National Insurance, workers are now facing incorrect wages due to problems with pension payments through superannuation.
It is understood the deduction was due to be made before April.
But a decision was made to delay the process.
Now, according to Unison, staff have had large deductions made in wages leaving many once again struggling financially.
A spokeswoman for the Department of Health confirmed there were "some errors" but could not clarify the number of people affected.
Unison, however, says it is now "inundated" with calls from people saying calculations are incorrect.
One nurse who works in the Royal Victoria Hospital told the Belfast Telegraph almost £400 was deducted from her wages.
"I just checked my account online and it is at least £384 out. I haven't received my pay slip yet but I'm paid the same every month, so something is very wrong," she said. The mother-of-four, who did not want to be named, said other colleagues had been struggling for months.
"My situation is nowhere near as difficult for some front line staff who have 20-hour contracts."
She added: "I know staff who have still not had the problems sorted out."
Ray Rafferty from Unison said it was another error in what had been a long line.
"It is another mess," he said. "What I am concerned about is this is the sixth or seventh issue that they are having with the payroll. The additional payments are being taken out in one go.
"That was supposed to take effect as of April 1.
"But because of the problems with payroll they didn't do it. Now, they're taking three months out at one time and there are major deficits for people as far as their pay is concerned.
"We already have staff to do additional hours and refusing to do work which isn't in the normal contracted hours because they are not being paid for it – that has an impact on provision of service and patient care."
Thousands of hospital workers across all trusts in Northern Ireland have been affected by incorrect payments for months.
It started last October after a new payroll system was introduced.
Technical difficulties with the system were blamed for the payroll problem.
The underpayments followed the centralisation of the payroll system by the Business Services Organisation.
Staff have not been receiving claims for overtime, travel claims and allowances.
In May the Department of Health said incorrect National Insurance contributions had been deducted from some people's pay, but steps had been taken to ensure it did not happen again.
A health service spokeswoman said staff were told in April that there would be a delay in implementation.
It was decided in May that implementation would be postponed until June to allow a validation exercise to be completed to ensure that the correct contributions were applied.
"Early indications from the June payroll would suggest that the vast majority of the 70,000 HSC staff have had the correct deductions made for pensions."
She added: "We are aware of some errors but these will be addressed promptly."