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How Does a Granny Flat Affect My Depreciation?

Published 26 June 2026 · Last updated 26 June 2026

Quick Answer

Adding a granny flat can significantly enhance your property's depreciation claims under Division 43 for capital works and Division 40 for plant and equipment. This addition typically allows you to claim depreciation on the new construction cost, potentially reducing your taxable income. However, specific rules apply, and it's advisable to consult a Chartered Quantity Surveyor to maximise your deductions.

Adding a granny flat to your investment property can be a strategic move, not only for increasing rental income but also for enhancing your depreciation claims. Understanding how this affects your tax deductions involves navigating both Division 43 for capital works and Division 40 for plant and equipment.

How Granny Flats Impact Depreciation

When you construct a granny flat, the cost associated with the building's structure falls under Division 43 of the Income Tax Assessment Act 1997. This allows you to claim a percentage of the construction costs each year over a 40-year period. Additionally, any new plant and equipment installed, such as appliances and fixtures, can be depreciated under Division 40. The most common misconception is that you can only claim depreciation on the main dwelling, but a granny flat can significantly enhance your overall depreciation benefits.

How This Works in Practice

Consider a scenario where you add a granny flat to your property in Melbourne for $150,000. The construction cost of the granny flat is eligible for Division 43 deductions at a rate of 2.5% per annum, equating to $3,750 annually. Additionally, if you spend $20,000 on new appliances and fittings, these can be depreciated under Division 40. Assuming an average effective life of 10 years for these assets, you could claim approximately $2,000 in the first year. If you're in the 37% tax bracket, this results in a tax saving of about $2,145 in the first year alone.

Professional Insight

In our experience, many investors overlook the potential depreciation benefits a granny flat offers. One thing we frequently see is investors underestimating the value of a depreciation schedule tailored to the new structures. What most investors don't realise is that even small additions to a property, like a granny flat, can result in substantial tax savings over time. Engaging a Chartered Quantity Surveyor to prepare a comprehensive depreciation schedule ensures you're claiming the maximum deductions possible.

When Does the Answer Change?

  • Post-9 May 2017 Properties: If you acquired a second-hand property after this date, you cannot claim Division 40 depreciation on previously used plant and equipment in the granny flat.
  • Pre-1987 Buildings: If your main property was built before 1987 and no substantial renovations have been done, you might not be able to claim Division 43 deductions for the main dwelling, but you can for the granny flat if it's new.
  • Properties in SMSFs: Depreciation rules can vary for properties held in a Self-Managed Super Fund, particularly regarding tax treatments and benefits.
  • Commercial vs Residential Use: If the granny flat is used for commercial purposes rather than residential, different depreciation rules may apply.

When Should You Seek Professional Advice?

You should seek professional advice when considering the installation of a granny flat to understand the full depreciation potential. A Chartered Quantity Surveyor can provide a tailored depreciation schedule that optimises your tax position. Additionally, consulting with an accountant ensures that your tax filing accurately reflects these deductions and complies with ATO regulations.

What to Do Next

  • Engage a Chartered Quantity Surveyor: Obtain a detailed depreciation schedule for your new granny flat.
  • Consult Your Accountant: Discuss how the additional depreciation will affect your overall tax strategy.
  • Review Property Insurance: Ensure your insurance covers the new structure and any increased rental income.
  • Document All Costs: Keep accurate records of all construction and installation expenses.
  • Evaluate Rental Market: Assess the potential rental income from the granny flat to maximise your investment return.
  • Plan for Future Upgrades: Consider the long-term maintenance and potential upgrades to retain or increase the property's value.
  • Frequently Asked Questions

    Can I claim depreciation on a granny flat built before 1987?

    If the granny flat was newly constructed, you can claim depreciation under Division 43, regardless of the main dwelling's age. However, if it was built before 1987 and hasn't been significantly renovated, claims may be limited.

    How does a granny flat impact my tax return?

    A granny flat increases your depreciation claims, which can reduce your taxable income. This is reflected in your tax return, potentially resulting in a larger refund or reduced tax payable.

    Does a granny flat affect the CGT cost base?

    Yes, adding a granny flat can increase the property's CGT cost base, potentially reducing the capital gain when you sell. It's advisable to maintain detailed records of all associated costs.

    Are there state-specific regulations for granny flats?

    Yes, regulations can vary by state, such as planning permissions and rental rules. It's important to check local council requirements before construction.

    What if the granny flat is used for Airbnb?

    The depreciation treatment remains similar, but income from short-term rentals like Airbnb may affect tax obligations differently. Consult with your accountant for specific advice.

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