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Understanding the Indexation Method for CGT in Australia

Published 26 June 2026 · Last updated 26 June 2026

Quick Answer

The indexation method for CGT in Australia adjusts the cost base of an asset for inflation, using the Consumer Price Index (CPI) to calculate the capital gain. This method is available for assets acquired before 21 September 1999. It can reduce the taxable gain by accounting for inflation over the holding period.

The indexation method for calculating Capital Gains Tax (CGT) in Australia allows investors to adjust the cost base of their asset to account for inflation. This method uses the Consumer Price Index (CPI) to increase the original purchase cost of an asset, effectively reducing the taxable capital gain. It's important to note that this method is applicable only to assets acquired before 21 September 1999. For assets purchased after this date, the discount method is generally used instead.

Under the indexation method, the cost base of the asset is increased by applying the CPI indexation factor from the quarter the asset was acquired to the quarter it was disposed of. This adjustment aims to ensure that only the real, inflation-adjusted gain is taxed, rather than any nominal increase in value due to inflation.

A common misconception among investors is that the indexation method applies to all assets, regardless of acquisition date. However, this method is strictly limited to pre-21 September 1999 acquisitions. Another confusion arises when investors try to apply both the indexation and discount methods simultaneously, which is not permissible.

To see how this plays out, consider an investor who purchased a residential property in Melbourne for $300,000 in March 1995 and sold it in March 2023 for $900,000. Using the indexation method, the cost base would be adjusted for inflation. If the CPI indexation factor increased the cost base to $450,000, the capital gain becomes $450,000 instead of $600,000. At a 37% marginal tax rate, this reduces the tax payable by approximately $55,500, providing significant savings.

In our experience reviewing thousands of properties across Australia, many investors overlook the benefits of the indexation method, especially those who have held properties for several decades. Additionally, there's a tendency to underestimate the complexity involved in calculating the correct CPI factor, leading to miscalculations. Another frequent oversight is failing to consider whether the property was used for income-producing purposes, which can affect CGT calculations.

The answer can differ depending on your situation. For example, if the property was acquired post-21 September 1999, the indexation method cannot be used. Similarly, if the property was held in a superannuation fund, different rules might apply. Partially income-produced properties may require apportioning the gain, and properties acquired by companies are not eligible for the CGT discount, which affects the decision to use indexation.

Given the complexities involved in applying the indexation method correctly, it is advisable to seek professional advice. A Chartered Quantity Surveyor can provide accurate cost base adjustments, while an accountant ensures compliance with tax laws and maximises your tax position.

Here are some practical steps you can take immediately:

  • Determine the acquisition date of your asset to check eligibility for the indexation method.
  • Obtain historical CPI data to calculate the correct indexation factor.
  • Consult with a Chartered Quantity Surveyor for an accurate cost base assessment.
  • Work with your accountant to ensure your CGT calculations are compliant and optimised.
  • Review your asset portfolio to identify other properties eligible for indexation.
  • Plan future property acquisitions with tax outcomes in mind.
  • Frequently Asked Questions

    Can I use the indexation method for properties bought after 1999?

    No, the indexation method is only available for assets acquired before 21 September 1999. For later acquisitions, the discount method is typically used.

    How do I calculate the CPI indexation factor?

    The CPI indexation factor is calculated by dividing the CPI at the time of disposal by the CPI at the time of acquisition. This factor is then applied to the original cost base to adjust for inflation.

    What happens if I used the property for both personal and rental purposes?

    If the property was used for both personal and rental purposes, the capital gain must be apportioned based on the period it was income-producing. This affects the CGT calculation.

    Does the indexation method apply in all Australian states?

    Yes, CGT rules including the indexation method apply uniformly across all Australian states and territories. State-specific property laws do not alter the CGT calculation.

    How does using the indexation method affect my tax return?

    Using the indexation method reduces the taxable capital gain by adjusting the cost base for inflation. This lower taxable gain is what you report on your tax return, potentially reducing your overall tax liability.

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