The ATO has revealed some of the most common mistakes people make at tax time. Assistant Commissioner Karen Foat said that errors range from honest mistakes to people deliberately over-claiming to increase their refund. 

The ATO says the top four mistakes to avoid are:

  • lodging before all prefill data is available or failing to report all income. Ms Foat said "we know from previous years that the early birds who lodge in the first weeks of July are far more likely to make mistakes or submit incomplete data";
  • claiming the wrong thing - work-related expenses is one area where people commonly make mistakes. To help taxpayers work out what they can claim, the ATO has developed 30 occupation guides for specific occupations; 
  • forgetting to keep receipts; and 
  • claiming for something never paid for – The Assistant Commissioner said the ATO often sees people "making claims at the record-keeping limit, thinking that the ATO will never question a claim if we don't require receipts. But you still need to have spent the money yourself and be able to show us how you've worked out your claim".

Source: https://www.ato.gov.au/Media-centre/Media-releases/How-to-nail-your-return/