At least 150 Australian Tax Office (ATO) staff were suspected of participating in a TikTok GST fraud that crippled the government agency.
A large number of suspicious income tax and GST refunds and fake businesses and identities were flagged at the tax office after a series of TikTok videos had promoted the fraud and attempted to recruit participants.
More than 57,000 people are believed to have participated in the fraud, fleecing the tax office out of $2 billion between April 2022 to June 2023.
The Australian National Audit Office discovered about 150 tax office staff were suspected of being involved in the scam as of October 2023.
Twelve of those were working with the tax office at the time of the suspected fraud and had action taken against them.
"This includes termination of contract, administrative action, and criminal prosecutions," the tax office said in a statement.
"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 majority of the remaining staff were former contractors and employees not working with the tax office at the time of the suspected fraud.
The criminal investigations have led to 100 arrests and 16 convictions.
Penalties of more than $120 million have been issued and the tax office has recovered $123 million of the $2 billion lost.
The tax office said the promotion of the fraud on social media caused the crime to spread at an "unprecedented rate".
"We have taken a range of compliance actions against more than 57,000 individuals, and our strategies have driven a continuous reduction in GST fraud attempts," it said.
"This includes, where appropriate, proceeds of crime referrals to the Australian Federal Police and departure prohibition orders to prevent people with significant tax debt from leaving the country."
The tax office maintained it had improved its defence against tax fraud and has taken measures to prevent future attempts.
The Australian National Audit Office has submitted five recommendations with its report, which the tax office has agreed to in full.
The full report can be read here.