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Capital Works Deduction: Impact on Your Cost Base Explained

Published 26 June 2026 · Last updated 26 June 2026

Quick Answer

A capital works deduction, under Division 43 of ITAA 1997, allows investors to claim tax deductions on construction costs of income-producing properties. This deduction reduces the cost base, impacting capital gains tax calculations when the property is sold. Properly understanding and applying these deductions can significantly affect your tax liabilities.

A capital works deduction, as outlined in Division 43 of the Income Tax Assessment Act 1997, allows property investors to claim deductions for construction costs on income-producing buildings. This deduction is applicable to structural improvements such as walls, floors, and roofs, and is claimed over a period of 25 to 40 years, depending on when the construction commenced. It's crucial for investors to understand how these deductions interact with the property's cost base, especially when calculating capital gains tax upon sale.

How Capital Works Deductions Affect Your Cost Base

Capital works deductions reduce your property's cost base, which is the original value used to calculate capital gains tax (CGT) upon sale. The cost base includes the purchase price, plus any costs incurred to acquire, hold, and improve the property. When you claim capital works deductions, the amount claimed reduces the cost base, potentially increasing the capital gain and thus the CGT payable when the property is sold. A common misconception is that these deductions are optional or insignificant, but they can substantially impact your tax outcome.

How This Works in Practice

Consider a scenario involving a 2010-built, 3-bedroom house in Melbourne purchased for $900,000. Over the years, the owner claims $150,000 in capital works deductions. Upon selling the property for $1.2 million, the cost base is adjusted from $900,000 to $750,000 due to the deductions. This results in a capital gain of $450,000. At a 37% tax rate, the CGT payable would be $166,500. If the deductions were not claimed, the cost base would be higher, reducing the capital gain and the tax payable.

Professional Insight

In our experience, many investors overlook the long-term impact of capital works deductions on their CGT liabilities. One thing we frequently see is investors not keeping thorough records of construction costs, which complicates deduction claims and cost base calculations. Another common issue is misunderstanding the eligibility of certain improvements under Division 43. What most investors don't realise is that failing to claim these deductions not only affects annual tax returns but can also lead to a larger-than-expected CGT bill upon sale. Additionally, we often advise clients to consider the timing of property improvements, as this can influence both deductions and the property's overall tax strategy.

When Does the Answer Change?

  • Pre-1985 Properties: Properties built before 19 September 1985 generally do not qualify for capital works deductions, impacting the cost base differently.
  • Partial Year Ownership: If you own a property for only part of the year, you can only claim deductions for the period it was income-producing.
  • Commercial Properties: These may have different rates and eligibility criteria for capital works deductions compared to residential properties.
  • Joint Ownership: If a property is jointly owned, deductions must be apportioned according to ownership interest, affecting each owner's cost base proportionately.

When Should You Seek Professional Advice?

You should seek professional advice when determining eligible construction costs, understanding how deductions will impact your cost base, and planning the timing of improvements. A Chartered Quantity Surveyor can provide a depreciation schedule, while an accountant can help integrate these deductions into your broader tax strategy. These professionals ensure compliance with ATO guidelines and maximise your tax benefits.

What to Do Next

  • Review your property records to identify eligible construction costs.
  • Engage a Chartered Quantity Surveyor to create a comprehensive depreciation schedule.
  • Consult with an accountant to understand the impact of deductions on your CGT liability.
  • Plan property improvements strategically to optimise tax benefits.
  • Keep detailed records of all property-related expenses and improvements.
  • Reassess your tax strategy annually to incorporate any changes in legislation or property use.
  • Frequently Asked Questions

    What types of construction costs are eligible for capital works deductions?

    Eligible costs include structural improvements like walls, floors, and roofs. Non-eligible costs are plant and equipment, which fall under Division 40.

    How does claiming capital works deductions affect my tax return?

    Claiming these deductions lowers your taxable income, resulting in tax savings. However, it also reduces your property's cost base, affecting CGT calculations.

    Are capital works deductions applicable to properties in all Australian states?

    Yes, capital works deductions apply nationally, but consult local regulations for any state-specific nuances.

    Can I claim capital works deductions on a property I live in?

    Deductions can only be claimed on income-producing properties. Owner-occupied homes do not qualify.

    What happens to my cost base if I stop claiming deductions?

    Your cost base is adjusted by the total deductions you could have claimed, not just those you actually claimed.

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