Model your capital gains tax before you sell
Compare up to three sale scenarios side-by-side. Adjust dates, costs, and discounts to see how your tax bill changes. Everything stays on your device.
Scenario worksheet
Scenario comparison
| Detail | Scenario A | Scenario B | Scenario C |
|---|---|---|---|
| Purchase price | $300,000 | $300,000 | $300,000 |
| Sale price | $450,000 | $480,000 | $510,000 |
| Total cost base | $321,000 | $321,000 | $321,000 |
| Holding period | 14 months | 20 months | 26 months |
| CGT discount | Yes | Yes | Yes |
| Capital gain | $129,000 | $159,000 | $189,000 |
| Taxable gain | $64,500 | $79,500 | $94,500 |
| Estimated tax | $20,963 | $25,838 | $34,965 |
What this estimator assumes
Australian resident individual
Calculations follow the rules for Australian tax residents. Companies, trusts, and foreign residents have different CGT treatments not covered here.
Asset acquired after Sep 1985
We assume the asset was purchased after 20 September 1985, when CGT was introduced. Pre-CGT assets are generally exempt.
No capital losses applied
This modeller does not offset capital losses from other assets. In practice, you can use capital losses to reduce your net capital gain.
Flat marginal rate
Tax is estimated using a single marginal rate you select. It does not include Medicare levy, offsets, or the progressive tax scale applied to your full income.
50% discount eligibility
The checkbox applies the 50% CGT discount for individuals holding the asset over 12 months. If unchecked, the full gain is taxable.
No indexation
For assets held over 12 months, individuals can choose either the 50% discount or indexation (frozen at Sep 1999). This estimator uses the discount method only.
How to think about your capital gains tax
Start with the basic formula
Capital gain equals your sale proceeds minus your cost base. The cost base includes the purchase price plus incidental costs like stamp duty, legal fees, and agent commissions. Sale costs are deducted from the proceeds. The result is your gross capital gain.
If you held the asset more than 12 months and you're an Australian resident individual, you can apply the 50% CGT discount. That means only half the gain gets added to your assessable income for the year.
Watch out for these common mistakes
- Forgetting purchase costs. Stamp duty and legal fees can be thousands of dollars. They increase your cost base and reduce your gain.
- Assuming the discount applies automatically. You must meet the 12-month holding period and be an individual or trust. Companies don't get it.
- Using the wrong tax rate. Your CGT is taxed at your marginal rate, not a separate CGT rate. The gain pushes your total income higher, which might push you into a higher bracket.
- Ignoring the Medicare levy. The 2% Medicare levy usually applies on top of your marginal rate. This estimator excludes it for simplicity.
- Overlooking the main residence exemption. If the asset is your home and you've lived in it the whole time, you probably don't pay CGT at all.
When to use this planner
This works best when you're weighing up whether to sell now or later, or comparing different sale prices. Run a few scenarios: sell at today's market value, sell after holding another 6 months, sell at a stretch price. The side-by-side comparison makes the trade-offs visible.
It's also useful when you're budgeting for tax after a sale. The estimate gives you a ballpark figure to set aside before you file your return.
Before you act on these numbers
This estimator is for educational planning. Tax law changes, and your personal situation might have details that change the outcome — other income, deductions, losses, or special exemptions. A registered tax agent can review your specific case and give you advice you can rely on.
The ATO website has current CGT information and worksheets. If your numbers are large or the asset type is unusual (collectables, foreign property, employee shares), professional help is worth the cost.