With the income tax deadline fast approaching, Australians who have yet to lodge their returns are running out of time. But rushing to beat the clock could prove an expensive mistake, with overlooked deductions, incorrect claims and unexpected tax bills potentially leaving taxpayers worse off.
For millions of Australians, completing an annual tax return is hardly the highlight of the year. It's one of those jobs that tends to get pushed to the bottom of the to-do list, particularly when work, family and running a business are competing for attention.
But with the 2 November deadline for lodging 2025–26 tax returns fast approaching, the temptation to rush through the process is growing.
That's understandable. Nobody wants to miss a deadline and potentially face a penalty from the Australian Taxation Office (ATO).
The problem is that a hastily prepared tax return can be just as costly as a late one. Missed deductions can mean paying more tax than necessary, while incorrect claims, forgotten income and simple administrative errors can result in unexpected tax bills, amended assessments and unwanted attention from the ATO.
For small business owners, sole traders and Australians juggling several sources of income, the risks are particularly significant.
The message is simple: getting your tax return right matters more than getting it done quickly.
Why the last-minute rush is risky
There's a big difference between completing a tax return and completing it properly.
When taxpayers leave everything until the final few days, they often rely on memory rather than records, guess at expenses or simply accept whatever information has been pre-filled into their return.
That's where problems begin.
The ATO receives information from employers, banks, health funds, government agencies and investment platforms, but that doesn't mean every item of income or every deduction is automatically accounted for.
Pre-filled information can be incomplete or incorrect, and taxpayers remain responsible for ensuring their returns are accurate.
Rushing also increases the likelihood of entering figures incorrectly, overlooking income or claiming expenses that don't meet the tax rules.
For business owners, the stakes are higher. A rushed return might overlook business income, misclassify capital expenditure as an immediate deduction or fail to properly account for GST, depreciation and business-use percentages.
A few extra hours spent reviewing the figures could save considerable time, money and stress later.
The deductions you might be missing
One of the biggest financial risks of rushing a tax return is overlooking legitimate deductions.
Most taxpayers are familiar with the obvious claims, such as work-related travel, uniforms and professional subscriptions. But there are plenty of other expenses that can be forgotten, particularly when records haven't been maintained throughout the year.
For employees who regularly work from home, deductions for eligible running expenses can add up. Depending on the method used, these might include electricity, internet, phone costs and stationery.
However, the ATO has strict record-keeping requirements. Under the fixed-rate method, taxpayers must maintain records of the actual hours worked from home, rather than simply estimating their hours at tax time.
Other commonly overlooked deductions include professional memberships, union fees, work-related training, income protection insurance premiums paid personally outside superannuation, and eligible expenses associated with managing investments.
For small business owners, the list is even longer. Business insurance, accounting fees, software subscriptions, advertising, bank charges and interest on business borrowings may all be deductible, provided the relevant requirements are satisfied.
Assets purchased for business use may also qualify for an immediate deduction under the applicable instant asset write-off rules, although eligibility, thresholds and timing requirements must be checked.
The danger of rushing is that smaller expenses, scattered across bank statements, invoices and receipts, are easily forgotten.
Individually, they might not seem significant. Collectively, they can make a substantial difference to the final tax bill.
Don't claim what you're not entitled to
Of course, the opposite problem is equally common: claiming too much. The ATO has become increasingly sophisticated in identifying deductions that appear excessive or inconsistent with a taxpayer's occupation, income or circumstances.
Work-related expenses remain a particular area of scrutiny. Some taxpayers assume that spending money on something connected with their job automatically makes it tax-deductible. Unfortunately, that's not how the rules work.
To claim an expense, you generally need to have incurred it yourself, not been reimbursed, and have a genuine connection between the expense and earning your assessable income. You also need appropriate records. For example, travelling from home to your regular workplace is generally private travel, even if you work unusual hours or carry a laptop.
Similarly, ordinary business clothing, such as suits or everyday office wear, isn't deductible simply because an employer expects staff to dress professionally.
Mobile phone and internet expenses are another common trap. If you use your phone for both work and personal purposes, you can only claim the work-related proportion.
Small business owners face similar issues with vehicle expenses, home office costs and purchases that have both private and business uses.
Claiming 100% of an expense when only part relates to business activities can lead to problems if the ATO reviews the return.
And while a generous deduction might initially produce a bigger refund, that benefit can quickly disappear if the claim is disallowed and interest or penalties are imposed.
The income you forgot to declare
It's not just deductions that cause trouble.
One of the most common reasons for an unexpected tax bill is failing to account for all sources of income.
Many Australians now earn money from more than one activity. Alongside their regular employment, they might operate a small online business, undertake freelance work, drive for a rideshare platform, rent out a room or sell products through digital marketplaces.
Others receive interest, dividends, capital gains or income from overseas investments.
These amounts can be easy to overlook, particularly when they're earned irregularly or paid into a different bank account.
But the ATO has extensive data-matching arrangements covering employment income, financial transactions, property dealings, cryptocurrency activity and online platforms.
For sole traders, an especially important point is that business income generally needs to be declared even if the activity is relatively small or undertaken alongside a full-time job.
There's no general exemption simply because the income comes from a side hustle.
And don't assume that because tax hasn't been withheld from a payment, the income isn't taxable.
In many cases, the absence of withholding simply means the tax liability will emerge when the return is lodged.
Why a refund can turn into a tax bill
Many taxpayers approach tax time expecting a refund, particularly if they've received one in previous years.
But circumstances change, and a refund is never guaranteed.
Someone who has taken on a second job, received a pay rise, earned investment income or started a business may discover that insufficient tax was withheld during the year.
For example, a taxpayer earning $80,000 from their main employment might also earn $15,000 from freelance consulting.
If no tax has been set aside from the consulting income, a significant additional tax liability could arise when the return is prepared.
Other surprises can come from capital gains on shares, investment properties or cryptocurrency, as well as changes to private health insurance rebates, Medicare levy surcharge liabilities and HELP repayments.
Taxpayers with outstanding government debts may also find that some or all of an expected refund is offset against those liabilities.
For business owners, there can be a further sting: additional tax arising from business profits may be accompanied by entry into the PAYG instalment system, creating future payment obligations.
The important thing is to understand the likely tax outcome before lodging, rather than assuming a refund is on its way.
Don't let the deadline become an expensive mistake
For taxpayers preparing their own 2025–26 return, the deadline is 11.59pm on Monday 2 November 2026. The usual 31 October deadline falls on a Saturday this year, giving taxpayers an extra couple of days.
Missing that deadline can result in failure-to-lodge penalties, although the ATO generally takes a more lenient approach where a taxpayer has a good compliance history or is due a refund.
But there's an alternative to rushing.
Taxpayers who engage a registered tax agent and are added to the agent's client list by 31 October may qualify for an extended lodgement deadline, potentially into May 2027. Not everyone qualifies, particularly those with outstanding prior-year returns, so it's important to check individual circumstances.
For anyone with complicated tax affairs, that extra time could be invaluable.
If a tax bill is likely, don't ignore it. Lodging the return and arranging a payment plan with the ATO is generally preferable to letting the problem escalate.
Five things to check before pressing submit
Before lodging, taxpayers should take a final look at five areas:
Income: Have you included all employment, business, investment, rental and other taxable income?
Deductions: Have you identified all legitimate expenses, checked the rules and retained the necessary evidence?
Personal circumstances: Have changes to your employment, investments, health insurance or HELP debt affected your tax position?
Business records: Have you reconciled your accounts, reviewed asset purchases and correctly separated private and business expenditure?
The final result: Do you understand why you're receiving a refund or facing a tax bill, and does the amount look reasonable?
If something doesn't make sense, investigate before lodging rather than hoping the ATO won't notice.
Tax time doesn't have to be stressful, but leaving everything until the last minute rarely produces the best outcome.
A little preparation can mean the difference between claiming everything you're legitimately entitled to and missing out. It can also prevent an apparently attractive refund from becoming a costly repayment obligation months later.
With the deadline looming, the temptation is to get the return lodged and move on.
But the real objective shouldn't simply be to beat the clock. It should be to lodge a return that's accurate, complete and delivers the best legitimate tax outcome.
After all, saving a few minutes today isn't much of a victory if it costs you hundreds or thousands of dollars tomorrow.