Capital gains tax is usually the largest single cost of selling an investment property, and since the May 2026 Federal Budget it has become the one where your purchase and sale dates matter most. This calculator gives you a quick, general estimate under both the current rules and the reformed rules that apply from 1 July 2027, including sales that straddle the changeover.

How the rules work

CGT runs on contract dates, not settlement dates. If you signed the purchase contract before 20 September 1985 the property is generally exempt. If you have held for less than 12 months, the whole gain is taxed with no discount. For sales with a contract date before 1 July 2027, the familiar rules apply: half the gain is taxed at your marginal rate once you have held for more than 12 months.

When a property has two owners, each owner is assessed on their own share of the gain at their own marginal rate. The shares come from the title: joint tenants hold 50/50, and tenants in common hold whatever shares were registered when they bought. For couples where one partner earns less, or has stepped back from paid work to look after the family, that structure has traditionally been valuable, because the lower earner’s share of the gain is taxed at their lower rate. Two things follow. First, the planning happens at purchase, not at sale: whose names go on the title, and in what shares, is locked in on day one. Second, the 2026 reforms blunt this advantage for gains that accrue after 1 July 2027, because the 30 per cent minimum rate applies to each owner regardless of their income, with an exemption only for pensioners and income support recipients. Gains accrued before that date keep the old treatment, which makes the timing of a sale a real consideration for couples with unequal incomes. The calculator above models all of this: switch it to two owners, set the split and each owner’s rate, and it will show the tax per owner.

From 1 July 2027, under the reforms legislated after the May 2026 Federal Budget, the 50 per cent discount is replaced for individuals by inflation indexation of the cost base, and capital gains are taxed at a minimum rate of 30 per cent regardless of your other income, with an exemption for pensioners and income support recipients. Properties owned across the changeover are split: gains accrued to 1 July 2027 keep the 50 per cent discount at marginal rates, and gains after that date fall under the new system, using either a valuation at 1 July 2027 or the ATO apportionment formula. New builds can elect between the discount and indexation.

The same budget also restricted negative gearing to new builds for properties purchased after 7.30pm AEST on 12 May 2026, with properties already held at that time exempt. If you are weighing up a purchase or a sale around these dates, the timing itself can be worth real money, in both directions.

Where to from here

If you are buying, our Investment Buyers page covers the budget changes, stamp duty, depreciation, and your obligations to tenants, and our blog on buying as an investor in Perth walks through the whole picture. If you are selling a tenanted property, start with our guide to selling a tenanted property, or contact us for advice on a specific property.

This page and calculator are general information only, not financial, legal, or tax advice. Thresholds, rates, and rules change, and your circumstances matter. Confirm your position with your accountant or the ATO before acting.