Edible underwear aficionados, gym junkies and aspiring adult entertainers have been put on notice over dodgy tax deductions, as some of Australia's weirdest expense claims are revealed.

As the ATO warns individuals and tax agents to avoid unwarranted and undocumented claims in annual returns this tax season, accounting giant H&R Block has published a new list of the most curious expenses clients have tried to claim while working with accountants.

Just how much breast enhancements contributed to Australia's $8.6 billion tax gap is unclear, but the firm said one female taxpayer tried to claim her improvements were a "tool of the trade".

The woman did not work as an adult performer and was unsuccessful in claiming the surgery was necessary for her work.

An Australian tradie who tried to claim costs for a European holiday, described as an exercise in "researching his craft".

Equally questionable was an Australian tradie who tried to claim costs for a European holiday, described as an exercise in "researching his craft".

Accountants also stopped a client's attempt to claim a deduction for edible underwear, as well claims for dog food for a client who occasionally took his pet to work to guard tools and equipment.

H&R Block director of tax communications Mark Chapman said in very limited circumstances taxpayers could claim the cost of acquiring an animal and costs for food, vet bills and other ongoing costs but the deductions were limited.

The basic rule for claiming deductions is expenses incurred as part of work can be added to a taxpayer's annual return.

Mr Chapman said the ATO was giving a heavy focus to deductions as part of compliance audits.

One client who occasionally took his pet to work to guard tools and equipment tried to claim for dog food.

"Remember the three golden rules for claiming deductions," he said.

"Only claim for an item of expenditure that relates to your job; don't make a claim if your employer reimbursed you for the expense; and you can only make a claim if you can prove you spent the money.

"So keep receipts, invoices and bank statements.

"Finally, if you're not sure if something is claimable or not, get advice from a tax professional and if you are entitled to a deduction, claim it."

A hairdresser was told she could not claim a transport deduction for taking her scissors and clippers to work.

Other questionable deductions politely blocked by agents included a taxpayer wanting to claim cigarettes which he said helped reduce stress levels, and a claim for sunscreen and an umbrella for a worker who said the location of his office forced him to walk to a park for a daily smoko.

A hair dresser was told her she couldn't claim the cost of travelling to and from work with scissors and clippers, at odds with legitimate deductions for workers transporting bulky tools and equipment.

A nightclub bouncer tried to claim the cost of martial arts courses, a potential breach of rules allowing professional athletes, police officers and defence personnel to claim some gym membership costs.

The claims pale in comparison to the 2016 case of an Australia IBM salesman who made $100,000 in bogus work claims, including his family grocery bill and $5000 in "secretarial services" from his 7-year-old son. Gary Ogden lost in court after claiming to have paid more than $5000 for secretarial services when in fact the son "sometimes ran upstairs to the study when the phone was ringing, answered the phone and then handed it to his father".

Administrative Appeals Tribunal deputy president Stephen Frost described Mr Ogden's behaviour as "disgraceful".

ATO analysis released this week found adjustments to work expense claims were required in 78 per cent of all agent-prepared tax returns, compared with 57 per cent of taxpayer-prepared returns.