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How Does Interest Deductibility Work for Investors?

Published 26 June 2026 · Last updated 26 June 2026

Quick Answer

Interest on loans used to acquire income-producing assets is generally deductible in Australia. Under the ATO guidelines, the purpose of the loan and the use of the borrowed funds are key. It's crucial to maintain clear records to substantiate claims.

Interest deductibility is a cornerstone of property investment in Australia, allowing investors to reduce their taxable income by claiming interest paid on loans used to acquire income-producing assets. According to the Australian Taxation Office (ATO), the primary consideration is the purpose of the loan, not the security. This means that even if a property is used as security for a loan, the interest is only deductible if the borrowed funds are used for income-producing purposes.

Under the ATO's guidelines, interest on loans to purchase rental properties, for renovations that enhance rental prospects, or to refinance existing investment loans, is typically deductible. However, common misconceptions arise, particularly when loans are mixed-use, such as part personal and part investment. It's critical to maintain clear records and apportion interest correctly based on the use of funds.

To see how this plays out in practice, consider a scenario where you purchase a 3-bedroom investment property in Melbourne for $800,000. Assuming a loan of $640,000 with an interest rate of 5%, your annual interest payment would be $32,000. At a 37% marginal tax rate, this could reduce your tax liability by $11,840 annually.

In our experience reviewing thousands of properties across Australia, we often see investors fail to properly apportion interest on mixed-use loans, leading to incorrect claims. Another frequent oversight is not adjusting interest claims when a property transitions from personal use to rental. Additionally, some investors mistakenly believe that interest during periods when a property is not rented is always deductible, which is not the case if the property is not genuinely available for rent.

The answer can differ depending on your situation. For properties purchased after 9 May 2017, if a property is initially used as a primary residence and later rented out, interest deductibility can only begin when the property becomes available for rent. Similarly, for properties held in a Self-Managed Super Fund (SMSF), different rules apply, and professional advice is essential. Joint ownership also requires careful apportionment of interest deductions based on ownership percentage.

Given the complexities involved, it's wise to consult both a Chartered Quantity Surveyor and an accountant. A QS can provide detailed insights into the apportionment of costs and ensure that all eligible deductions are claimed, while an accountant can offer advice tailored to your tax situation.

  • Review your loan agreements to determine the purpose of each loan.
  • Ensure accurate record-keeping of all interest payments and apportion interest on mixed-use loans.
  • Consult with a Chartered Quantity Surveyor to maximise your deductions.
  • Speak with your accountant to align your tax strategy with your investment goals.
  • Regularly review your property portfolio to adjust interest claims as circumstances change.
  • Consider the tax implications of refinancing or altering loan structures.
  • Frequently Asked Questions

    Is interest on a home loan deductible if the property is rented out part-time?

    Interest is deductible only for the period and portion of the loan used to produce rental income. You must apportion interest based on time rented and use.

    Can I claim interest on a loan used for property renovations?

    Yes, if the renovations are for an income-producing property. Keep detailed records to substantiate the purpose and extent of the renovations.

    How does interest deductibility work for properties in an SMSF?

    Interest is deductible if the loan is for acquiring or maintaining income-producing assets within the SMSF. Consult a professional for SMSF-specific advice.

    Are there state-specific rules for interest deductibility?

    Interest deductibility is governed by federal tax law, so state-specific rules do not apply. However, state taxes and regulations may impact overall investment returns.

    How do I report interest deductions on my tax return?

    Report interest deductions in the rental schedule of your tax return. Ensure all claims are substantiated by documentation and align with the ATO guidelines.

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    Written by Koste Team · Koste Chartered Quantity Surveyors · AIQS Member · RICS Member · TPB Registered · 1300 669 400 · info@koste.ai