The tax return mistakes that cost you

I was at a barbecue in October, beer in hand, and a mate told me he had just done his tax return through myGov in 25 minutes. Proud of himself. I asked him a few questions. By the third question (about the working-from-home days he had not bothered to claim) it was clear he had left somewhere north of $900 on the table. He is not stupid. He is busy and he assumed the ATO's pre-fill was correct, which it is, for the things it knows about. The things it does not know about are exactly the things that would have lowered his bill.

This is the pattern I see across most men I know. Salaried, busy, vaguely competent with money, treating tax as an annual chore rather than a financial decision worth two hours of focused attention. The cost of that pattern, averaged across the men in their forties I have actually checked, is somewhere between $800 and $1,800 a year of overpaid tax.

These are the specific mistakes. Each one has a fix. None of the fixes are aggressive or grey. They are claims and elections you are entitled to make under standard ATO rules.

Mistake one: missing the WFH deduction

Working from home deductions exist in two forms in 2026, and most blokes pick the wrong one or do not claim at all.

• Fixed-rate method (67 cents per hour). Covers electricity, gas, internet, phone, stationery, computer consumables. Requires a record of hours worked from home (a timesheet or a calendar; no phone-and-internet bills needed because the rate already incorporates them).
• Actual cost method. Calculate the actual portion of bills attributable to working from home. More paperwork. Often produces a higher claim for someone with a dedicated office room and high running costs (heating, cooling, premium internet).

For a man working from home 2 days a week (16 hours), 48 weeks a year, the fixed-rate method gives 67c x 16 x 48 = $515 a year. At a 32.5 percent marginal rate, that is $167 of tax saved. At 37 percent, $190.

Common errors:

• Not claiming at all because "I have a job, I do not have a home office."
• Claiming actual cost without the supporting records, which falls over in an audit.
• Forgetting to claim depreciation on the desk, chair, monitor, laptop bought during the year. These are separate from the fixed-rate method and can be claimed on top of it.

Two minutes with a calendar at the end of the year recovers most of this. The depreciation on a $400 ergonomic chair plus a $300 monitor stand bought in March is roughly $200 a year for several years and stacks on top of the WFH hours rate.

Mistake two: missing the small-business super contribution offset

This one applies to anyone with a side business or contracting income, which is more men than you would think (uber, weekend renovation work, paid speaking, advisory fees, side consulting).

If your employer is paying you SG and you also earn assessable income from non-employment sources, you can make a personal deductible super contribution against the non-employment income. The deduction comes off your taxable income at your marginal rate, and the contribution is taxed at 15 percent inside super. The differential is the saving.

For a man with $120,000 of salary and $25,000 of contracting income, putting $20,000 of the contracting income into super as a personal deductible contribution saves roughly $7,400 in tax (37 percent marginal rate minus 15 percent contribution tax, on $20,000) while also moving the money into a tax-advantaged structure for the long run.

The trap: you have to file a Notice of Intent to Claim form with your super fund before lodging the tax return that includes the deduction. Get the timing wrong and the deduction is denied. The form is a one-page PDF on every super fund's website. Fill it in, get the acknowledgement, then lodge.

Mistake three: wrong main residence treatment after separation

This is the one that catches divorced men hard, because the rules are not intuitive and the conversation usually happens at a moment when you are not at your sharpest.

The main residence exemption from CGT applies to your principal place of residence. After separation, complications start:

• If you move out and your former spouse stays in the house with the kids, you can elect to continue treating that house as your main residence for up to 6 years for CGT purposes (the "absence rule"). But you cannot also claim main residence on a new property during that period.
• If you and your spouse own two properties, one each, post-separation, you must elect which is the main residence. The choice has CGT consequences for both of you.
• If the former matrimonial home is sold as part of a property settlement, the CGT consequences depend on who gets the proceeds and what the holding history was. Family law settlements include CGT rollover provisions that defer rather than eliminate the tax.

The mistake men make is to assume the divorce paperwork sorts the tax. It does not. The CGT consequences need to be modelled separately, and the elections need to be made at the right time. A two-hour session with a tax agent who has seen this before saves an enormous amount of grief.

Mistake four: investment property mis-claims

Negatively geared investment properties are a national sport, and the deductions are frequently claimed incorrectly. The errors I see most:

• Claiming the cost of repairs as a deduction when it is actually a capital improvement. Replacing a worn carpet with the same type of carpet is a repair (deductible). Replacing carpet with hardwood floors is an improvement (depreciable over years, not deductible immediately).
• Missing the depreciation schedule. A quantity surveyor's depreciation schedule for a recently built investment property is often $400 to $700 to commission and produces $4,000 to $8,000 of depreciation deductions in year one. The ROI is obvious and most landlords still skip it.
• Claiming travel costs to inspect the property. This was disallowed in 2017. Stop claiming it.
• Missing the borrowing-cost amortisation. Loan establishment fees, mortgage insurance, and broker fees can be deducted over 5 years (or the loan term, whichever is shorter). Most men forget to add these to the schedule in subsequent years.

If you have an investment property and you are not using a tax agent, you are almost certainly leaving money on the table. The $400 the agent costs is recovered in the first 30 minutes of the consultation.

Mistake five: forgetting CGT on shares

The ATO data-matches your share trades through CHESS and the major broker reporting feeds. They know what you sold. If you do not declare it, an amended assessment arrives a year later with interest and a shortfall penalty.

Common errors:

• Forgetting that ETF distributions include realised capital gains that flow through to your tax return. The annual tax statement from the ETF issuer breaks this down. Most blokes glance at the dividend amount and skip the rest.
• Misapplying the 50 percent CGT discount. The discount applies if you held the asset for more than 12 months. Day-counting matters. Holding from 5 March to 4 March of the following year does not qualify. 5 March to 5 March does.
• Not using carry-forward capital losses from previous years. If you sold something at a loss in a prior year and reported it correctly, the loss carries forward and can be applied against a current-year gain. Many men forget to apply it.
• DRP (dividend reinvestment plan) confusion. Reinvested dividends are taxable in the year they are reinvested, even though you did not receive cash. The cost base of the new shares is the reinvestment price.

Why a registered tax agent is worth $250

If your tax situation is "salary and that is it," myGov is fine and the pre-fill will give you most of what you need. For anyone with anything beyond a single salary (investment property, share trading, side income, recent separation, salary-sacrifice arrangements, super contributions, complex deductions), a registered tax agent at $250 to $400 is the highest-ROI professional service in your year.

What you get for the money:

• Catches deductions you would have missed. In my experience this alone returns 3 to 5 times the fee on average.
• Lodges through the agent portal, which gives a 4-month-later due date than self-lodgement.
• Reviews prior year returns for amendments if errors are found. Up to 4 years back for individuals.
• Provides written advice on grey areas, which is a defence if the ATO queries the return later.
• Documents the substantiation properly so an audit is a paperwork exercise, not a panic.

Pick an agent who is registered with the Tax Practitioners Board (verify on the TPB public register) and who has seen returns like yours before. The local sole practitioner who has been doing this for 25 years usually outperforms the chain shopfronts.

USE A TAX AGENT IF YOU HAVE ANYTHING BEYOND WAGES. The pretence that you can DIY this is costing you more than the agent ever would.

The bullet summary

• Working from home. 67c per hour fixed rate, plus depreciation on equipment, every year.
• Side income. Personal deductible super contribution, with Notice of Intent filed before lodgement.
• Post-separation. Sort main residence elections deliberately, with advice.
• Investment property. Get a depreciation schedule, distinguish repairs from improvements, do not claim travel.
• Shares and ETFs. Declare distributions in full, apply the 12-month rule precisely, use carry-forward losses.
• Tax agent. Worth it if you have anything beyond wages.

A tax return is not a chore. It is a financial decision that you make once a year, in the same room you do other important paperwork, with two hours of focus.

Two hours saved a thousand. Use them well.