What the calculator does
Two scenarios, same inputs:
- Pre 1 July 2027 (current law). The capital gain is reduced by the 50% CGT discount under s 115-100 ITAA 1997 (assumes the property is held more than 12 months). The discounted gain is added to other taxable income and taxed at marginal rates.
- Post 1 July 2027 (proposed reform). The gain is taxed in full at marginal rates with no discount. If marginal-rate tax on the gain would be less than 30% of the gain, the 30% minimum tax floor applies.
What it doesn't do
The calculator simplifies in three ways the full Byrz engine handles:
- It doesn't split the gain. Under the proposed reform, gains accrued before 1 July 2027 retain current treatment; only the post-2027 portion gets the new rules. The split is based on the property's valuation as at 1 July 2027 - not a calculation a 2-input form can do.
- It doesn't index the post-reform portion. The reform reintroduces CPI indexation for the post-2027 cost base, so only real (inflation-adjusted) gains are taxed. This calculator taxes the nominal gain.
- It doesn't cover non-individual structures. SMSF accumulation has a 1/3 discount; SMSF pension has a 0% rate; companies have no discount. The calculator assumes individual ownership.
Caveats
The 30% minimum tax floor and the CGT split mechanic are proposed as of late 2026 - not law. Final legislation, regulations and ATO guidance may change the scope, the floor rate, or the start date.
For a calculation that handles the CGT split, indexation, structure-specific treatment, and the rest of the picture (cashflow, alternative structures, hold-vs-sell timing), see the full $49 Byrz property report.