The Biggest Mistake Aussies Make at Tax Time in 2026 — and How to Avoid It

Quick answer: The ATO's single biggest concern at tax time is Australians over-claiming work-related expenses — particularly those that are either private in nature, lack receipts, or never happened at all. The fix is straightforward: only claim what you genuinely spent for work, keep your records, and don't copy last year's deductions without checking whether they still apply.

Every July, millions of Australians rush to lodge their tax returns — and every year the Australian Taxation Office (ATO) flags the same pattern of errors. In 2026, the message from the ATO is blunt: the biggest mistakes taxpayers make are "entirely avoidable." They're not complex accounting traps. They're basic errors around deductions, income reporting, and record-keeping that cost people money — either through missed refunds or, worse, through audits, penalties, and repayment demands.

Here's what the ATO is watching for this tax season, what the rules actually say, and how to make sure your 2025–26 tax return is accurate, complete, and defensible.

Why the ATO Is Paying Extra Attention in 2026

The ATO has significantly increased its data-matching capabilities in recent years. It now cross-references information from banks, employers, share registries, rental platforms, private health insurers, and government agencies before your return is even lodged. By the time you click submit, the ATO often already knows your salary, your bank interest, your dividend income, and whether you sold an investment property.

That means errors — whether accidental or deliberate — are increasingly likely to be caught. The ATO's pre-fill data (which auto-populates sections of your myTax return) is more comprehensive than ever, but it also creates a false sense of security. Pre-fill is not infallible, and you are still legally responsible for every figure on your return.

The ATO has publicly stated that it pays particular attention to:

Work-related expense claims that look unusually high for someone's occupation
Rental deductions that don't align with rental income reported
Capital gains that appear in bank records but not on returns
Income from side hustles, the gig economy, and cryptocurrency

The Number One Mistake: Over-Claiming Work-Related Deductions

The ATO has been consistent about this for years, and 2026 is no different. Work-related expense claims are the most common source of error in Australian tax returns — and the errors almost always go in the taxpayer's favour, which is precisely why the ATO scrutinises them so closely.

What counts as a legitimate work-related deduction?

To claim a work-related deduction, you must satisfy three conditions:

You spent the money yourself — it wasn't reimbursed by your employer.
It was directly related to earning your income — not a private or domestic expense.
You have a record to prove it — a receipt, invoice, bank statement, or other evidence.

If your claim doesn't tick all three boxes, you shouldn't be making it.

The specific deductions the ATO flags most often

Working from home (WFH) expenses have been a flashpoint since 2020, and the ATO is still seeing claims that don't hold up. From 1 July 2023, the ATO revised the fixed-rate method for WFH deductions to 67 cents per hour. This rate covers electricity, internet, phone, and stationery. You can no longer claim those expenses separately if you use the fixed rate — many taxpayers still do, which results in double-dipping.

To use either WFH method (fixed rate or actual cost), you must keep a record of the hours you actually worked from home. A vague estimate of "I worked from home most days" won't satisfy the ATO.

Clothing and laundry is another persistent problem. You can only claim the cost of occupation-specific clothing, protective clothing, or uniforms that are registered with AusIndustry. Claiming the cost of a suit, business casual wear, or any clothing you could reasonably wear outside work is not allowed — regardless of whether you only wear it to work.

Car expenses are also frequently over-claimed. The two methods for claiming car use are:

Method	How it works	Record required
Cents per kilometre	Flat rate of 88 cents/km in 2025–26, up to 5,000 km	Written record of km and work purpose
Logbook	Actual vehicle expenses × work-use percentage	12-week logbook, odometer records

The ATO specifically warns against claiming the full cost of a car that's partly used privately, or claiming travel from home to work (which is generally a private expense, not a work-related one).

Self-education expenses can be deducted if the course directly relates to your current role and helps you maintain or improve your specific skills. You cannot claim education that leads to a new career — even if that career is related to your industry. For example, a nurse undertaking a nursing degree can claim; a retail worker undertaking a nursing degree generally cannot.

The Second Mistake: Not Reporting All Income

While over-claimed deductions grab most of the headlines, under-reported income is equally on the ATO's radar — and the consequences are more serious because it can look deliberate.

Income sources people forget to declare

Bank interest: With cash savings rates at elevated levels following the RBA's rate cycle, many Australians earned meaningful interest on their savings accounts and term deposits in 2025–26. This is taxable income. It will appear in your pre-fill data, but it's worth checking that the figures are complete — especially if you hold accounts with multiple institutions.

Dividends and managed fund distributions: If you own shares or ETFs directly (not through super), any dividends or distributions paid to you during the year must be declared. This includes franking credits (a tax offset attached to dividends from Australian companies), which must be included as income before the offset is applied. Use our Income Tax Calculator to see how dividends and franking credits affect your overall tax position.

Cryptocurrency: The ATO treats crypto as an asset, not a currency. If you sold, swapped, gifted, or used cryptocurrency during the 2025–26 year, you likely triggered a capital gains tax (CGT) event. The ATO has data from Australian crypto exchanges and is actively looking for unreported gains. If you held crypto for more than 12 months before disposing of it, you may be entitled to a 50% CGT discount.

Gig economy and side income: Income from Uber, Airtasker, Airbnb, Etsy, OnlyFans, and any other platform is taxable. The ATO receives data from many of these platforms directly. If you rent out a room or a property through Airbnb, the income must be declared — and you can claim deductions for expenses associated with that income, but only in proportion to the time and floor space used for rental purposes.

Lump sum payments: Redundancy payments, insurance payouts, and government grants may have specific tax treatment — some portions may be tax-free, others assessable. If you received any unusual lump sum during the year, check the ATO's website or speak to a registered tax agent.

The Third Mistake: Assuming Pre-Fill Is Complete

Pre-fill is genuinely useful — it saves time and reduces data-entry errors. But it has limits that catch people out every year.

Pre-fill data typically includes your PAYG (Pay As You Go) payment summaries from employers, Centrelink payments, bank interest (from participating institutions), and some private health insurance data. It does not reliably include:

Income from overseas sources
Cash income (freelancing, babysitting, tutoring)
Crypto gains
Rental income from private arrangements
Interest from non-participating financial institutions
Capital gains from property sales

Additionally, pre-fill data often arrives progressively throughout July and August. If you lodge your return on 1 July, some employer or bank data may not yet be available. The ATO recommends waiting until late July for most pre-fill data to load before lodging.

Note: Lodging early is not always better. An incomplete return lodged on 1 July often results in the ATO issuing a notice of amended assessment later — which delays your refund and can cause confusion.

The Fourth Mistake: Treating Tax Deductions as a Shopping List

A common mindset the ATO warns against is treating tax deductions as a reward for spending money. Claiming a deduction means you recover the tax you paid on that income — it does not mean the ATO pays for your purchase.

Here's a simple example:

Suppose you're in the 32.5% marginal tax bracket (applicable to taxable income between $45,001 and $135,000 in 2025–26). If you spend $500 on a legitimate work expense, your tax refund from that deduction is $162.50 — not $500. You're still $337.50 out of pocket.

This matters because some Australians spend money specifically to "get a tax deduction" — buying equipment they don't need, prepaying expenses unnecessarily, or claiming items that sit on the boundary of work and personal use. If the expense isn't genuinely work-related, there is no legitimate deduction to claim.

The Fifth Mistake: Poor Record Keeping

The ATO doesn't audit every return — but if yours is selected, you need to be able to substantiate every claim. "I'm pretty sure I spent about $800 on work stuff" is not a defence.

What records you need to keep

Expense type	Minimum record required
Work-related purchases under $300 (combined claim)	Written record explaining work purpose
Work-related purchases over $300	Receipt or invoice with supplier name, date, amount, and nature
Car expenses (logbook method)	12-week logbook + odometer readings
WFH (fixed rate)	Diary or log of hours worked from home
Rental property expenses	Invoices, receipts, and bank statements for all costs
Capital gains	Purchase and sale contracts, brokerage records

You must keep records for five years from the date you lodge your return — not five years from when you made the purchase.

The ATO's myDeductions tool (within the ATO app) lets you photograph receipts and record car trips throughout the year. Using it makes tax time vastly simpler and ensures you have records if you're ever asked to substantiate a claim.

Rental Property: A Dedicated Problem Area

Australians with investment properties consistently appear on the ATO's list of concern areas. The most common rental property mistakes include:

Claiming the full interest deduction when the loan is partially private. If you refinanced and took out extra cash for a holiday, home renovation, or other private purpose, only the portion of interest related to the investment property is deductible.

Claiming capital works as immediate deductions. Structural improvements to an investment property (new roof, extension, new kitchen) are generally deducted at 2.5% per year over 40 years under Division 43 — not as an immediate expense. Repairs and maintenance to restore something to its original condition can generally be claimed immediately, but improvements cannot.

Claiming deductions for periods the property was personally used. If you or a family member stayed at the property for two weeks during the year, you cannot claim 100% of deductions for that year. The deductible portion must be reduced proportionally.

Getting the land tax treatment wrong. Land tax is a deductible expense for investment properties in most states — but the rules differ significantly across jurisdictions. Use our Land Tax Calculator to understand your obligations and ensure you're claiming the correct amount.

What Triggers an ATO Audit?

The ATO uses sophisticated data analytics to identify returns that look unusual. While the full methodology is not public, common triggers include:

Deductions that are disproportionately high relative to income for your occupation
Sudden large increases in claimed deductions year-on-year without obvious explanation
Rental losses that are very high relative to rental income
Capital gains omitted despite data-matching evidence
Income that doesn't match information from third-party sources (employers, banks, platforms)

If the ATO selects your return for review, it will typically write to you asking you to substantiate specific claims. You'll have a set period to respond with evidence. If you can't provide evidence, the claim will be disallowed and you may be liable for the additional tax plus interest and potentially a penalty.

The best defence is a simple one: only claim what you're entitled to, and keep the paperwork.

How to Get Your 2025–26 Return Right

Follow these steps to give yourself the best chance of a correct return and a smooth tax season:

Wait until late July before lodging, to allow pre-fill data to populate.
Check your pre-fill data carefully — don't assume it's complete.
Gather your records — receipts, invoices, logbooks, WFH diary, rental statements.
Only claim expenses you can document and that genuinely relate to your income.
Declare all income, including interest, dividends, crypto, side hustle revenue, and rental income.
Use the ATO's occupation-specific deduction guides — these outline what's claimable for your job type and help you avoid claiming what's not appropriate.
Consider using a registered tax agent — particularly if your situation is complex (investment property, shares, crypto, business income, or a capital gain). Tax agents have until May 2027 to lodge returns for their clients, which can also provide extra time.

If you want to understand how your income, deductions, and tax offsets interact before you lodge, our Income Tax Calculator lets you model different scenarios and estimate your refund or liability.

Frequently Asked Questions

What is the ATO's biggest concern at tax time in 2026?

The ATO's primary concern is over-claimed work-related deductions — particularly expenses that are partly private, lack supporting records, or don't directly relate to the taxpayer's income-producing activities. The ATO describes these errors as "entirely avoidable."

Do I need receipts for deductions under $300?

Not necessarily a physical receipt, but you do need a written record that describes what you spent, when, and why it was work-related. For individual items over $300, a receipt or invoice is required. Note that the $300 threshold applies per item, not as a total cap on unsubstantiated claims.

Can I claim my home internet if I work from home?

If you use the fixed rate method (67 cents per hour), internet costs are already included in that rate — you cannot claim them separately. If you use the actual cost method, you can claim the work-related portion of your internet bill, but you need records to demonstrate the proportion used for work versus personal use.

Is cryptocurrency taxed in Australia?

Yes. The ATO treats cryptocurrency as property, and any disposal (sale, swap, gift, or purchase of goods) triggers a capital gains tax event. If you held the asset for more than 12 months, you may be entitled to a 50% CGT discount. All crypto transactions must be declared on your tax return.

What happens if I make a mistake on my tax return?

If you realise you've made an error after lodging, you can request an amendment through myTax or by writing to the ATO. It's always better to correct an error voluntarily than to wait for the ATO to find it — voluntary amendments typically attract lower penalties. If the ATO identifies the error first and determines it was reckless or intentional, penalties can be significant.

How long does the ATO have to audit my return?

For most individuals, the ATO has two years from the date of assessment to review a return. If there is suspected fraud or evasion, there is no time limit. For taxpayers with more complex affairs (business, trusts, or international transactions), the window may be four years. This is why keeping records for five years from the date of lodgement is recommended.

Should I use a tax agent or lodge myself?

This depends on your situation. If you have straightforward PAYG income with simple deductions, myTax is genuinely capable. If you have a rental property, investment portfolio, capital gain, crypto, a business, or any unusual income or expense, a registered tax agent is likely worth the cost — and their fee is itself tax-deductible in the following year.

Related Calculators and Guides

Income Tax Calculator — estimate your tax liability, refund, and effective tax rate for 2025–26
Capital Gains Tax Calculator — work out CGT on shares, crypto, or property
Rental Income Tax Calculator — calculate tax on rental income after allowable deductions
Negative Gearing Calculator — see whether your investment property generates a tax loss
Land Tax Calculator — understand your land tax obligations by state
HECS-HELP Repayment Calculator — calculate your compulsory student loan repayments

This article is for general information only and does not constitute financial, tax or legal advice. Individual circumstances vary. Consult a registered tax agent or licensed financial adviser before making decisions based on this information.