Capital Works Deduction Calculator (Division 43) Australia

What the capital works deduction calculator does

The capital works deduction calculator works out the annual building write-off you can claim under Division 43 on an income-producing property in Australia. You enter the eligible construction cost, choose the building type and construction period, set your ownership share and the number of days the property produced income, and the tool returns the deduction for the year, the statutory rate that applied, the write-off period, how much of the cost is left to claim, and an estimate of the tax the deduction saves you at your marginal rate.

Capital works is often the largest single deduction on a rental property and the one most frequently missed, because it is not a cash expense. Nothing leaves your bank account, yet the deduction reduces taxable income exactly like rates, insurance or interest do.

How Division 43 works

Division 43 of the Income Tax Assessment Act 1997 lets you deduct the construction cost of a building over a fixed period, rather than immediately. The rate is statutory, not a matter of judgement: the ATO sets it by the class of building and the date construction started, and it does not change with the property's value, your purchase price, or how much you paid for it.

Two rates do most of the work. The 2.5% rate spreads the construction cost over 40 years and applies to residential rental buildings where construction started after 15 September 1987, along with most non-residential buildings and structural improvements started after 26 February 1992. The 4% rate spreads the cost over 25 years and applies to residential construction that started between 18 July 1985 and 15 September 1987, and to certain traveller accommodation and manufacturing buildings.

Because the rate fixes the period, the write-off period in the result is simply the inverse of the rate: 1 divided by 2.5% gives 40 years, and 1 divided by 4% gives 25 years. Once the period is up, the deduction stops: the cost has been fully written off, and the tool returns nothing further to claim.

What the calculation does

The tool runs a short sequence:

• It takes the eligible construction cost and multiplies it by your ownership share, giving your share of the cost.
• It multiplies that by the statutory rate for the building type you chose, giving the full-year deduction.
• It apportions the full-year figure by the days the property was income-producing, so a property rented for part of the year claims a part-year amount.
• It subtracts any full years you have already claimed, caps the total claim at the construction cost, and reports what is still to come.
• It applies your marginal rate, including the Medicare levy, to estimate the tax the deduction saves.

On a A$250,000 construction cost for a post-1987 residential rental, fully owned and rented all year, the deduction is A$6,250 a year for 40 years. For someone on a 32% marginal rate that is about A$2,000 of tax saved each year, and roughly A$120 a week of taxable income sheltered.

Working out the construction cost

The construction cost is the single input that matters most, and it is not the price you paid for the property. It is the original cost of building the structure, excluding land. Eligible expenditure covers the structural shell and permanently fixed elements: foundations, framing, brickwork, roofing, internal walls, tiling, sealed driveways, fences, retaining walls and in-ground pools. Professional fees such as engineering and architectural costs that relate to the build are included, along with structural improvements made later, like an added carport or a new deck.

What is excluded is just as important. Land is never included. Nor is demolition, soft landscaping, or the removable assets in the property. Carpets, curtains, blinds, ovens, dishwashers, air conditioners and hot water systems are plant and equipment, depreciated under a different set of rules over their own effective lives, and should not be added to the capital works figure.

If you bought an established property and do not know what it cost to build, you cannot simply estimate it yourself. A quantity surveyor's depreciation schedule is the accepted way to establish the figure, and it splits capital works from plant and equipment for you. That report is itself deductible.

Ownership share and part-year use

Where a property is owned jointly, each owner claims in line with their legal interest, not in line with who paid the expenses. A half-share of a property means half the deduction, which is what the ownership share field applies.

The days field handles the other common adjustment. Capital works is deductible only for the part of the year the building was used to produce income. A property rented from 1 July but withdrawn for a six-month renovation claims roughly half the full-year amount. A holiday home genuinely available for rent for part of the year is treated the same way. Days when the property was used privately, or was not genuinely available for rent, do not count.

Reading your result and the CGT catch

The output shows the deduction for the year, the tax saving at your marginal rate, the statutory rate and period, what you have claimed in earlier years, and what remains. The chart splits your share of the construction cost into claimed, current year, and still to claim, so you can see how far through the write-off you are.

One consequence deserves attention. Capital works deductions you have claimed generally reduce the property's cost base for capital gains tax, so the same dollars that lowered your taxable income each year can lift the taxable gain when you sell. That is usually still a good trade, because the annual deduction comes off income at your full marginal rate while an eventual gain on an asset held over twelve months may qualify for the CGT discount. It is a timing and rate difference, not a reason to skip the claim, but it is worth knowing before you sell.

When to use this tool

This calculator is useful when you want to:

• Estimate the capital works deduction on a rental or commercial property before lodging.
• Check the figure on a quantity surveyor's schedule.
• See how a part-year rental or a joint ownership share changes the claim.
• Understand how many years of deductions are left on an older building.
• Weigh the annual tax benefit against the cost-base reduction on a future sale.

Run it once when you buy and again in any year the property's use changes. The result is a planning estimate: your actual deduction depends on your records, the correct construction date, and how the property was used, so confirm the figures with a registered tax agent or a quantity surveyor before you lodge.

This is general information only and not financial advice.

About This Capital Works Deduction Calculator

Use this capital works deduction calculator to get an instant, accurate estimate. The figures follow official ATO guidance and every rate and threshold is kept up to date for 2026. Adjust the inputs above to match your situation, or browse all our calculators to plan your next step.