The Department of Finance has reported itself to the Fair Work Ombudsman and says it is working “as quickly as possible” to repay the staff.
Staff were contacted on Wednesday night informing them workers across two pay levels had not been paid an award they were entitled to.
“We are auditing the pay of all EOA-01 and EOA-02 staff employed during the relevant periods over the past four years, including former employees,” the email read.
“We have engaged KPMG to verify our proposed approach and to certify all payments to staff are correct.
“We expect this audit will be completed and back pay will be made to all affected staff by the end of the current financial year.”
In another email, the department confirmed it would include interest in the back payments, and had sought legal advice to ensure tax implications were managed.
In a statement to NCA NewsWire on Thursday, the department confirmed about 60 staff were affected.
It did not yet know how much money was owed.
“Finance has commenced an audit which will examine payroll records to verify the number of former employees affected and determine monies owed,” it said.
“Finance identified the issue and has self-reported this issue to the Fair Work Ombudsman.”
Finance Minister Simon Birmingham said the department had taken “swift and appropriate” measures to repay the money.
“Any underpayment is unacceptable and should be rectified as soon as it is identified,” he said.
The Community and Public Sector Union said it was “seriously concerned” about the underpayments in an email to staff, pledging to fight for “every cent” of owed money to be returned.
“These underpayments have seen staff who are already at the lowest pay levels paid less than the award rate. They are predominantly women, and work hard every day assisting members of the public,” it said.
It is unclear when the department became aware of the issue.
“The issue arose due to the interaction between the Australian Government Industry Award 2016 and the Commonwealth Members of Parliament Staff Enterprise Agreement 2016-2019 in relation to Electorate Office A employees,” it said.