How this calculator works

A capital gains tax (CGT) calculator estimates the net capital gain you include in your tax return when you dispose of an asset such as shares or an investment property. It compares what you received, the capital proceeds, with what the asset cost you, the cost base, then applies any losses and, if you are entitled to it, the CGT discount.

The result is not a separate tax at a flat rate, under the current rules. The net capital gain is added to your other taxable income and taxed at your marginal rates, plus any Medicare levy that applies. From 1 July 2027, that method changes for gains that accrue from that date, as explained in CGT old versus new rules.

The Never Lose Interest calculator is for shares and property held as CGT assets. Crypto has its own crypto tax calculator explainer. This page follows the ATO's official steps, including the worked examples of Rhi's investment property and share sale, last updated 29 June 2026.

This is general information only. It is not personal advice or a tax assessment, and it does not take into account your objectives, financial situation or needs.

How does a CGT calculator work?

For each CGT event, the calculator:

  1. works out the capital proceeds
  2. works out the cost base, or the reduced cost base if you made a loss
  3. subtracts the cost from the proceeds, to get a capital gain or a capital loss for that asset
  4. repeats the steps for every event in the year
  5. subtracts capital losses, including net losses carried forward from earlier years, from the capital gains
  6. applies the CGT discount, if you are entitled to it, to any remaining discountable gain
  7. shows the net capital gain, or a net capital loss to carry forward

You pay tax on a net capital gain at your marginal income tax rate, plus any Medicare levy. A net capital loss cannot be deducted from salary or wages. It can be carried forward and used against later capital gains.

If you have both discountable and non-discountable gains, the ATO says you can choose which gains to apply losses against first, and that it is usually better to apply them first to gains that are not eligible for the discount.

The CGT event for a sale of property generally happens on the contract date, not on settlement. In the ATO's example, contracts exchanged on 4 June 2026 and settled on 6 July 2026 belong in the 2025-26 return.

What are capital proceeds and the cost base?

Capital proceeds are what you receive when you sell the asset, or when another CGT event happens, such as an insurance payout if the asset is destroyed. If you give an asset away, or sell it to a friend for less than it is worth, the proceeds are generally the market value.

The cost base is what it cost you to acquire the asset, plus certain other costs of acquiring, holding and disposing of it. For property, that commonly includes the purchase price, stamp duty and conveyancing on the way in, and agent's commission and conveyancing on the way out. For shares, it commonly includes the purchase price and brokerage.

If you acquired the asset before 21 September 1999, you can, in some cases, index the cost base for inflation up to that date instead of using the 50% discount. The ATO notes that this can give a lower net gain in some circumstances, for example if you also have capital losses. You cannot use both indexation to 1999 and the discount on the same gain.

Assets acquired before 20 September 1985 are generally pre-CGT, and a capital gain or loss on the original asset is usually disregarded, subject to later events and any improvements that can have their own CGT treatment. A calculator should ask for the acquisition date for that reason.

How does the 50% discount work?

Under the current rules, Australian resident individuals, and trusts, can generally reduce a capital gain by 50% if they owned the asset for at least 12 months. You apply losses first, then the discount to the remaining eligible gain. Companies cannot use the discount. Complying super funds use a 33.33% discount.

The 12 months is counted against the particular asset, or parcel, you disposed of. Selling shares you bought 11 months ago does not qualify, even if you have held other parcels of the same company for years.

The ATO also notes that if you used a property for affordable rental housing, the discount can be up to 60%, under the official rules for that concession.

From 1 July 2027, the 50% discount is replaced, for gains that accrue from that date, with cost base indexation and a 30% minimum tax on real gains, for individuals, trusts and partnerships that have held the asset for at least 12 months. Gains that accrued before 1 July 2027 can still get the 50% discount if you were entitled to it. A calculator that applies a flat 50% to a sale after that date, without splitting the pre- and post-change portions, will be wrong for assets you already hold. The ATO said, in its 29 June 2026 update, that those Budget changes do not apply to Tax Time 2026, and that further resources would be available later.

How is CGT worked out on an investment property?

The ATO's Rhi example is a useful check on a calculator.

Rhi buys an investment property for $500,000 and sells it five years later for $600,000. She has no other capital gains or losses. The cost base is $530,000, made up of:

  • the $500,000 purchase price
  • $15,000 stamp duty
  • $1,200 conveyancing on purchase
  • $1,300 conveyancing on sale
  • $12,500 agent's commission

The capital gain is $600,000 minus $530,000, which is $70,000. Because she is an Australian resident and owned the asset for at least 12 months, the 50% discount reduces the net capital gain to $35,000. She reports a capital gain of $70,000 and a net capital gain of $35,000, and she pays tax on the $35,000 at her marginal rate.

If, in the same year, she also sells shares at a $4,500 loss (bought for $10,000 including stamp duty and brokerage, sold for $5,500), she applies that loss before the discount. The remaining gain is $65,500, and after the 50% discount the net capital gain is $32,750.

A calculator should also let you adjust for:

  • capital improvements that form part of the cost base
  • capital works deductions already claimed, which can reduce the cost base
  • a partial main residence exemption if the property was your home for part of the time, or if you used it to produce income
  • your ownership share, if the title is joint

Your main residence is generally exempt if you lived in it throughout the ownership period, it is on land of two hectares or less, and you did not use it to produce income. There are absence rules and partial-exemption methods if those conditions are not fully met, which are covered in the main residence CGT exemption guide. A standard investment-property calculation should not apply a full main residence exemption.

Buying costs such as stamp duty are dealt with in more detail in the stamp duty explainer. A net rental loss in earlier years is a separate income tax deduction, not a substitute for the cost base, as explained in how negative gearing works.

How is CGT worked out on shares?

The same steps apply. The cost base usually starts with what you paid, including brokerage and any stamp duty, and the proceeds are the sale price after any selling brokerage that forms part of the calculation.

If you bought the same shares in several parcels, at different times and prices, you need records that identify the parcel you sold. That identification sets the cost base and whether the 12-month holding period is met. Taxation Determination TD 33 says that for identical assets you decide which parcels are being disposed of and keep records that support the decision, and that first-in, first-out has been accepted as a reasonable basis. Average cost is generally not acceptable, except for identical assets acquired on the same day.

Dividend reinvestment plans create new parcels, usually at the market value of the shares acquired. Those parcels have their own acquisition dates. Bonus shares, returns of capital and takeovers can also change the cost base. If the transaction is more involved than a simple on-market sale, check the ATO's share CGT guidance or get advice rather than forcing it into a basic calculator.

What should a calculator leave out, or ask you to add?

A basic calculator will not, on its own, settle:

  • whether the main residence exemption, or a partial exemption, applies
  • the 2027 split of a gain between the discounted pre-change portion and the indexed post-change portion, until the official method and tools are in place
  • deceased estates, which the ATO says you cannot run through its online CGT tool
  • assets held in a company, trust or SMSF, which have different rates and rules
  • whether you are carrying on a business of share trading, in which case the income tax rules for business income can apply
  • foreign resident CGT settings, which can limit the discount and change which property is in scope

Enter Australian dollar amounts. Convert foreign currency at the time of each transaction, using a reasonable official or externally sourced rate, consistent with the approach described in the crypto tax calculator explainer.

Frequently asked questions

Do I pay CGT when I sell my own home?

Often no, if it has been your main residence for the whole period you owned it and you meet the other official conditions. If you rented it, used it for a business, or the land is more than two hectares, a full exemption may not apply.

Can I use a capital loss against my salary?

No. A net capital loss can only reduce capital gains, in the same year or in later years.

Is the 50% discount automatic after 12 months?

It is the usual rule for Australian resident individuals, trusts and partnerships, after losses have been applied, under the current law. It does not apply to companies, to assets held for less than 12 months, or to a gain if you chose 1999-style indexation instead. From 1 July 2027, different settings apply to later gains.

When do I report the sale of a property?

In the income year of the contract, not the year of settlement, if those dates fall in different financial years.

Does the calculator replace the ATO's tool?

No. The ATO has its own CGT calculator and record-keeping tool, and it remains the official working check. Never Lose Interest is a guide to the same arithmetic.

General information warning

This article, and the Never Lose Interest CGT calculator, are general information only. They are not personal advice, tax advice or a calculation of your notice of assessment. They do not take into account your objectives, financial situation or needs. The 2027 CGT changes are law, but some implementation tools were still being developed as at November 2026. Consider speaking with a registered tax agent before you lodge a return that includes a material share or property sale.

Sources

Last reviewed: November 2026.