The Tax Office (ATO) has confirmed that fraudsters have hacked at least four tax agents to access taxpayers' personal information.
However, the Australian Tax Office says the agents that were hacked only had 20 customers between them.
"It has been reported today that taxpayer information is at risk after criminals stole the identity of four tax agents," the ATO said in a statement.
"The report suggested that all Australian taxpayers' information was under threat.
This is incorrect." The ATO says the agents' sign-ins to the ATO system have now been cancelled, and the personal information of taxpayers who complete their own returns has not been compromised.
"We are working with the affected tax agents to ensure their practices and information is secure," the ATO added.
Tony Greco, the senior tax adviser with the Institute of Public Accountants, says they have also advised tax agents to keep their systems secure.
"The issue here is agents' digital certificate security being breached.
Once you get into an agent's database or portal access you have access to all their clients," he said.
"So in that case their tax file numbers could be compromised and a lot of personal information becomes accessible."