The biggest mistakes Australians make "every single year" on their tax returns have been revealed. Tax time is just weeks away, and Aussies are being warned these easy mistakes could cost them hundreds on their refund.

Tax Invest Accounting director Belinda Raso told Yahoo Finance she sees taxpayers getting caught out by these mistakes every year. This could be because they have rushed their tax return and done it as soon as July 1 hits, or simply because they don’t have all the information at hand.

“A big one is that we automatically go for a shortcut and a shortcut is never in taxpayers' favour,” she said.

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Here are the top five mistakes to watch out for.

1. Work from home deductions

If you are claiming work from home deductions, most Aussies forget to work out both methods to ensure they get the biggest possible deduction.

The fixed rate method lets you claim 70 cents for each hour worked from home. The actual cost method requires you to calculate the additional expenses you incur when working from home.

It is more onerous, but could give you a better deduction.

Raso said people who claimed the fixed rate method often forgot they could make separate claims for expenses the method doesn’t cover. The method only covers internet, mobile, electricity, gas, stationery and printing costs.

“So all of your computer equipment, the hardware, the software, your cords, cables, extensions, powerboards, your furniture, everything in that home office is going to be claimable,” she said.

“People that are working from home, even if they are hybrid, are losing hundreds of dollars per year on this alone.”

2. Medicare Levy Surcharge

Taxpayers report to the ATO whether they are liable for the Medicare Levy Surcharge. The ATO will also change people’s tax returns if they are liable and don’t declare it.

For the 2024-25 financial year, the threshold to pay the surcharge is $97,001 for singles and $194,001 for families.

Raso said she sees mistakes with people saying they are liable for the surcharge, when they actually aren't.

This is usually single parent households who think they are classified as singles, but are actually classified as families even if their child isn't living with them.

“The average person could end up paying an extra $1,000 by not actually understanding these rules,” Raso said.

Taxpayers can amend their returns if they have made a mistake and they have up to two years less one day from the notice of assessment.