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Tax Time: 7 Common Tax Return Mistakes That Could Cost You Money

July 12, 2026

Tax Time 2026: 7 Common Tax Return Mistakes That Could Cost You Money

Every tax season, thousands of Australians either miss out on legitimate deductions or receive unexpected enquiries from the Australian Taxation Office (ATO). In most cases, these issues are avoidable with good preparation and professional advice.

At Gavin Ma & Co, we prepare tax returns for employees, investors, business owners, property investors and self-managed super fund (SMSF) members. Over the years, we’ve identified several common mistakes that can delay refunds, increase tax liabilities or lead to unnecessary amendments.

Here are seven of the most common tax return mistakes—and how you can avoid them this tax season.

1. Lodging Your Tax Return Too Early

Many taxpayers are eager to lodge their tax return as soon as the new financial year begins. While it’s understandable to want your refund quickly, lodging too early can create problems.

Many employers, banks, managed funds, health insurers and government agencies continue reporting information to the ATO throughout July. If you lodge before this information is available, your tax return may be incomplete.

We’ve regularly assisted clients who lodged early and later needed to amend their return after receiving dividend statements, managed fund tax reports or updated income information.

Waiting until your income information is complete can help reduce errors, avoid amendments and often results in a smoother assessment.

2. Forgetting Income That the ATO Already Knows About

The ATO’s data-matching systems have become increasingly sophisticated. Information is received directly from employers, financial institutions and investment providers, making it much easier for the ATO to identify omitted income.

Income commonly forgotten includes:

  • Interest from savings accounts
  • Share dividends
  • Managed fund distributions
  • Rental property income
  • Cryptocurrency transactions
  • Foreign income
  • Capital gains from selling investments
  • Income earned through ride-sharing or online platforms

Even small amounts of omitted income may trigger an amendment or review. Before lodging, it’s important to ensure all income sources have been included.

3. Claiming Deductions Without Proper Evidence

Many taxpayers assume that if an expense relates to work, it is automatically deductible. Unfortunately, this isn’t always the case.

Generally, you can only claim a deduction where:

  • You personally paid for the expense;
  • The expense directly relates to earning your assessable income; and
  • You have records to support your claim.

Receipts, invoices and digital records remain essential. If an expense has both private and work-related use, only the work-related portion is deductible.

Good record keeping not only supports your claims but also provides peace of mind should the ATO request further information.

4. Overlooking Investment and Rental Property Deductions

Investment income often creates additional tax opportunities, but also increases complexity.

Property investors should carefully review items such as:

  • Loan interest
  • Property management fees
  • Council rates
  • Insurance
  • Repairs and maintenance
  • Depreciation
  • Capital works deductions

Similarly, investors holding shares, exchange-traded funds (ETFs) or managed funds should ensure all distributions and capital gains are correctly reported.

We frequently see taxpayers overlook investment-related deductions or misunderstand the tax treatment of capital improvements versus repairs.

Professional advice can often identify deductions that might otherwise be missed.

5. Incorrect Working From Home Claims

Working from home continues to be common across many industries.

Although home office expenses may be deductible, taxpayers must keep appropriate records and apply the correct calculation method.

Depending on your circumstances, deductible expenses may include:

  • Electricity
  • Internet
  • Mobile phone usage
  • Office equipment
  • Computer accessories

Maintaining accurate records throughout the year makes preparing your tax return significantly easier.

6. Small Business Owners Waiting Until the Last Minute

For business owners, tax time is much easier when bookkeeping has been kept up to date throughout the year.

Before preparing your tax return, consider reviewing:

  • Bank reconciliations
  • Payroll records
  • Superannuation payments
  • Business expenses
  • Motor vehicle records
  • Asset purchases
  • Director loan accounts
  • GST reporting

Accurate financial records reduce errors and allow more time for tax planning opportunities before lodgement.

7. Trying to Do Everything Yourself

Tax law changes every year. Between capital gains tax, investment income, business deductions, rental properties, trusts and superannuation, many taxpayers are surprised by how complex their affairs have become.

Professional tax advice is no longer just about lodging a return—it is about ensuring your affairs are structured correctly and identifying opportunities to legally minimise tax.

Many of our clients discover that professional advice saves considerably more than the cost of engaging an accountant.

How Gavin Ma & Co Can Help

At Gavin Ma & Co, we provide taxation and accounting services tailored to individuals, families, investors and businesses throughout Australia.

Our services include:

  • Individual income tax returns
  • Rental property taxation
  • Capital gains tax advice
  • Business tax compliance
  • Trust and company taxation
  • Self-Managed Super Fund (SMSF) taxation
  • Tax planning strategies
  • ATO reviews and dispute assistance

Our objective is not simply to prepare your tax return—we aim to help you understand your tax position, remain compliant and identify opportunities to improve your long-term financial outcomes.

Ready for Tax Time?

Whether your tax affairs are straightforward or involve investments, rental properties, business income or an SMSF, obtaining professional advice can help ensure your return is accurate and complete.

If you’re looking for experienced tax accountants who provide practical advice and personalised service, the team at Gavin Ma & Co is here to help.

Contact Gavin Ma & Co today to arrange your 2026 tax return or tax planning consultation.