Assistant Commissioner Karen Foat said errors ranged from honest mistakes to people deliberately over-claiming to increase their refund.

She said incorrect work-related expense claims have been highlighted as a key driver of the $8.7 billion tax gap generated by individuals not in business.

The ATO has explained four particularly common mistakes to avoid this tax time.

Ms Foat said it was OK to lodge early if people had all the information they needed to do their returns accurately, but data from previous years indicated those who lodged in the first weeks of July were far more likely to make mistakes or submit incomplete data, potentially resulting in delayed refunds or debts to the ATO if information needed to be corrected.

"This tax time will see our sophisticated data-matching systems process an unprecedented amount of information and will track money moving around the economy," she said.

"We will be analysing over 650 million pieces of data from banks and financial institutions, employers, the sharing economy, rental property managers, cryptocurrency exchanges and share registries.

"Our data-matching will help us match what you've earned, whether from a traditional 9-5 job, a casual position or sharing economy income.

"Failing to declare all your income will result in you ending up with a bill when we later match your data."

Let the ATO make tax time an easier process for you by waiting a few weeks before lodging.

Work-related expenses is one area where people commonly make mistakes. To help you work out what you can claim, the ATO has developed 30 occupation guides and accompanying posters for specific occupations (ato.gov.au/occupations).

Remember, to claim a deduction for work-related expenses, follow the three golden rules:

You can only claim the work-related portion of expenses. You can't claim a deduction for any part of the expense that relates to personal use.

"Many people rely on advice from friends and co-workers on what is an acceptable claim, and the information may not always be accurate," Ms Foat said.

"This sees the ATO rejecting thousands of ineligible claims each year for things like gym memberships, travelling to and from work, conventional clothing and the private portion of phone and internet costs."

The ATO refuses a large percentage of claims where taxpayers are unable to produce records or receipts when asked. Even if the value of a claim is below the record-keeping threshold, you may be asked to show how you calculated your claim.

"Do away with the shoebox and try myDeductions in the ATO app instead - it's the easiest way to store your receipts. The deduction details can even be uploaded into your tax return or sent on to your tax agent," Ms Foat said.

"We often see people making claims at the record-keeping limit, thinking that the ATO will never question a claim if we don't require receipts," Ms Foat said.

"But you still need to have spent the money yourself and be able to show us how you've worked out your claim. If you can't explain it, we won't accept it, and we may penalise you for failing to take care when lodging your tax return.

"Exceptions to the record keeping rules are there to make things simpler - they do not allow you to claim an automatic deduction up to the specified amount where the money has not been spent.

"No one is entitled to a 'standard deduction'.

"A little bit of over-claiming across a lot of people adds up to billions of dollars. No matter how small, claiming deductions you are not entitled to means essential community services miss out."

Visit ato.gov.au for more information about what you can and can't claim, or to log in to myGov to lodge or check the progress of your tax return.

Otherwise, you can consult with your tax agent to see if they can assist with your query as well.