The ABC has admitted underpaying about 2500 casual staff over the past six years, sparking a review of how workers were short-changed.
The national broadcaster on Thursday admitted there had been an error calculating penalties, allowances and loadings for flat-rate casual staff.
"This error should not have occurred and the ABC apologises to any casual employee who has been underpaid," it said in a statement.
"The ABC is actively working to remedy this for affected employees as soon as possible."
Current and former casual staff were being notified about the error, the ABC added.
Management were alerted to the issue by the Community and Public Sector Union, prompting a referral to the Fair Work Ombudsman.
