“People try to claim a deduction or over-claim a deduction where they’re not actually entitled to,” Mr Chapman said.

“You’re only allowed to claim a personal deduction if you meet the 10 per cent rule, so basically if you’re employed, you’re not really able to claim additional personal contributions over and above what your employer has already made."

Mr Chapman said lack of awareness about allowable deductions for property is a recurring issue.

“It’s very easy to either miss, for instance, the capital works deductions if you don’t know that it even exists,” Mr Chapman said.

H&R Block also issued a general warning to taxpayers that they run the risk of incurring significant penalties from the ATO if they lodge their own tax return.

Under the current self-assessment system, taxpayers face large fines if they incorrectly claim deductions and do not declare income, said H&R Block.

Mr Chapman added that the system leaves taxpayers who lodge their own returns vulnerable to making mistakes and facing the consequences.

“This means, in effect, taxpayers can claim ‘anything within reason’ but if the claims are found to be incorrect, the taxpayer is required to repay the tax avoided, plus pay interest on incorrect claims at around 9.5 per cent per annum.

“If the ATO office believes that the taxpayer has acted carelessly, a penalty between 25 per cent and 95 per cent of the tax avoided may also be charged,” he added.

H&R Block has issued a list of common mistakes the group says taxpayers must look out for, including not declaring all income; alienation of personal services income; failure to claim excess imputation credits; failure to claim the senior Australian tax offset; and claiming tax deductions for items that are used in part for work and in part personally.