The Australian Taxation Office (ATO) says it is going over every tax return lodged, looking for incorrect and fraudulent claims.

Assistant Commissioner Karen Foat says taxpayers who are doing the right thing, and only claiming what they are entitled to, that they have nothing to fear from a potential audit.

But for people who have done the wrong thing, even if over-claiming by a little, her advice is that the best thing they can do is to fess up sooner rather than later.

“Each year the ATO contacts around two million people about their returns. In most cases, audits are not our first action,” she said this week.

“Third party data indicating under reported income, and deductions that appear high compared to people with a similar job and income level, tend to raise concerns.”

Tax Institute president Tim Neilson says anyone the ATO audits should be wary.

“Any taxpayer, individual or small business who finds themselves being audited by the ATO should seek the assistance of a properly qualified tax practitioner,” Mr Neilson told the ABC.

“Navigating an audit could be tricky, so it is wise to have the expertise of a tax professional who has walked this path before on your side.”

Some of the more questionable claims that raise red flags with the ATO include deductions for uniforms in an unlikely work environment and inappropriate claims for a private vehicles used for work.