Up to 150 Australian Taxation Office staff have been investigated for suspected involvement in a social media scam that ripped off $2 billion.
In an auditor-general's report into fraud management of the GST, the tax office revealed it sacked some employees and launched criminal investigations into others who were linked to the widespread rort.
The ATO workers were investigated as part of Operation Protego, set up to target people who benefited from fake GST refunds.
The operation was set up after the tax office received a large increase in refund fraud tip-offs, as well as an increase in the number of Australian business number and GST registrations.
Social media videos also offered advice on how people could claim more money through GST refunds.
The auditor-general report said those suspected of claiming false GST refunds had tried to claim amounts between $38,900 and $2.4 million.
"The ATO has identified 57 per cent of individuals involved in the fraud were in receipt of a government benefit," its report said.
"Approximately 30 per cent of individuals attempted to obtain a fraudulent refund a second time and 10 per cent attempted a third time."
Since the operation was set up, more than $2 billion has been reclaimed by the tax office, while a further $2.7 billion was stopped from being transferred just before payment was made.
As of August 2023, more than 100 arrests had been made, with 16 convictions.
It's estimated more than 57,000 people tried to claim the false refund.
The report said among those were 150 tax office staff, who were investigated by the ATO's internal fraud team.
"A range of treatment strategies have been applied by the ATO, including termination of employment and criminal investigations."
More than $120 million of financial penalties have been issued to people found to have taken part in the fraudulent scheme.
A spokesman for the ATO said the majority of the 150 people linked with the tax office were former contractors or former employees, who were not working for the tax office at the time.
Action was taken against 12 people who were substantiated as having committed fraud.
"This includes termination of contract, administrative action and criminal prosecutions," the spokesman said,
"As a result of our actions, we are not aware of anyone currently working at the ATO who is suspected of committing the fraud."
The tax office spokesman said the ATO had zero tolerance for fraud and corrupt behaviour.
"We expect all ATO staff and contractors to act with the highest level of integrity and we will take all the reasonable measures to prevent, detect and deal with fraud and corruption risk to the ATO."