Property calculator
CGT Cost Base Calculator
Model the CGT cost base indexation method with your own property figures, compare the taxable gain outcome, then email the stored report.
The recent budget has introduced important changes to how Capital Gains Tax (CGT) may be calculated. Use this calculator to estimate your potential CGT under the proposed rules.
Use this calculator to see how your CGT may change under the new budget rules. It compares the current 50% discount method with the proposed indexation approach. Simply enter your property details to estimate your cost base, capital gain and the potential reform value as at 30/06/2027.
Calculator inputs
Enter the property details and inflation settings.
* Reform value is system-derived using proportional growth. Actual valuation as of 30 June 2027 may differ and can be adjusted.
Interactive settings
CGT indexation scenario
Taxable capital gain by ownership years
Scenario breakdown
Old Rules Pre-Reform · 50% CGT Discount
Nominal GainRaw capital gain before any tax method: Sale Price − Purchase Price.
$500,000
Sale − purchase price
Indexed Cost BaseYour cost base grown by CPI from 1 Jul 2027 to the sale date. A higher indexed base means less taxable gain.
N/A
Not applicable
Phase 1 Taxable GainTaxable portion of the gain accrued before 1 Jul 2027, calculated using the 50% CGT discount.
$250,000
Pre-reform period
Phase 2 Taxable GainTaxable gain accrued after 1 Jul 2027: Sale Price minus the Indexed Cost Base. Zero if the sale is fully pre-reform.
$0
Post-reform period
Total Taxable Capital GainEstimated taxable capital gain only. Final tax payable depends on your marginal income tax rate and is not calculated here.
$250,000
Ownership: 15.4 yrs
Scenario comparison
Calculated using your purchase & sale price. Reference dates shown per scenario.
| Feature | Your scenarioScenario 1: Old Rules(Pre-Reform) | Scenario 2: New Rules(Post-Reform) | Scenario 3: Transitional(Straddling Reform) |
|---|---|---|---|
| Relevant Dates | Purchased 1 Jan 2011Sold 12 May 2026 | Purchased 1 July 2027Sold 1 July 2037 | Purchased 1 July 2024Sold 1 July 2034 |
| CGT Method | 50% CGT Discount | Cost Base Indexation | 3.00 years at 50% CGT discount7.00 years at Cost Base Indexation |
| Purchase Price | $500,000 | $500,000 | $500,000 |
| Sale Price | $1,000,000 | $1,000,000 | $1,000,000 |
| Nominal Gain | $500,000 | $500,000 | $500,000 |
| Indexed Cost Base | Not applicable | $671,985Cost + 3% inflation per year | $649,918Phase 2 base starts at $649,918 (value at 1 Jul 2027) |
| Phase 1 Taxable Gain(pre-reform period) | $250,000(50% of nominal gain) | $0(Not applicable) | $74,959(50% of the $149,918 gain accrued to 1 Jul 2027) |
| Phase 2 Taxable Gain(post-reform period) | $0(Not applicable) | $328,015(Sale minus indexed cost base) | $200,667(Sale minus indexed Phase 2 base) |
| Total Taxable Capital Gain | $250,000 | $328,015 | $275,626 |
This calculator estimates taxable capital gain only and does not calculate final tax payable or replace professional tax advice.
Note
- The calculator does not consider acquisition costs.
- The calculator does not consider selling costs.
- The calculator uses a formula to estimate the property value as at 30th June 2027; however, this value can be adjusted in the “Reform Value” field.
- The calculator assumes the property is an established property.
Disclaimer
This calculator is for general information and educational purposes only. The results are estimates based on assumptions and may not reflect your actual tax position. Tax laws and budget proposals may change, and individual circumstances vary. Please consult your accountant or financial advisor before making any investment or tax decisions.
