A simple answer to a not-so-simplequestion: “does this still work for me?”

It takes the inputs your accountant would normally need — purchase price, sale price, holding dates, marginal rate — and computes both the old-rules tax payable (50% CGT discount, no indexation) and the new-rules tax payable (indexed cost base, 30% minimum effective rate, no discount on established property). Then it shows you the difference in plain English.

For purchases before 1 July 2027 with a sale after that date, we split the calculation: the portion of the gain accrued before the cut-off is taxed under the old rules; the portion after is taxed under the new rules. The split uses a market valuation at the cut-off date.

• Indexation. We use the Australian Bureau of Statistics quarterly CPI series for historical periods, and your CPI assumption for forward periods. The indexation factor is rounded to three decimal places, consistent with ATO practice.
• 30% minimum effective rate. Applied to the gross capital gain (after indexation), independent of your marginal rate. Where your marginal rate produces a higher liability, the marginal rate prevails.
• Carried losses, stamp duty, depreciation. Excluded from the MVP. We surface this clearly in the disclaimer. Future versions will accept these as advanced inputs.
• Currency. All figures in Australian dollars, rounded to the nearest dollar.

It is not financial advice, not tax advice, and not a substitute for your accountant. Tax law has many edge cases — main residence partial exemptions, deceased estates, foreign-resident treatment, trust structures — that we deliberately do not model in the MVP. If your situation involves any of these, please use the tool as a conversation starter, not a conclusion.

Two of us. A property economist who got tired of explaining the changes one dinner party at a time, and a designer-engineer who wanted to make the maths legible. We’re not affiliated with any real-estate agency, mortgage broker, or political party. If you want to know more or have feedback, write to hello@proptax.au.