How we work out every number

The engine is written in plain code, with no AI anywhere in the calculations. It's covered by more than 290 automated tests, and every rate in it is tied to a published source with the date it takes effect. When a rule changes, the rate, the test that checks it and the rates page change together. Last reviewed 4 October 2026.

Tested against Treasury's worked examples

Treasury published worked examples for the 2026 reforms in its Budget explainer and in the draft apportioning determination. Our test suite reproduces each one.

The differences all come from one rule. Section 960-275(5) of the Income Tax Assessment Act 1997 says the indexation factor is "worked out to 3 decimal places". Treasury's examples use the unrounded factor; we follow the Act. On Jane's sale that's $217.

Capital gains tax

• Sales before 1 July 2027: 50% discount on the whole gain for individuals who've held the asset 12 months or more.
• Sales after, of property held on 30 June 2027: the gain to 30 June 2027 keeps the discount (Subdivision 112-E). The value on that date is either a market valuation or Treasury's draft apportioning method: the purchase price grown at one daily compounding rate from purchase to sale, counting days inclusive.
• Growth after 30 June 2027: cost base indexed by CPI from 1 July 2027 (s110-36(1A), s960-275(1B)), no discount. Losses use the unindexed reduced cost base.
• 30% minimum tax: a top-up of 30% of the post-2027 gain less ordinary tax on that slice (Division 119), not applied to anyone on an income support payment that year.
• New residential dwellings: the cheaper of the 50% discount on the whole gain and the indexed method.
• Quarantined rental losses come off the pre-2027 gain first, then the later gain, before any discount.
• Capital works deductions reduce the cost base. The CGT event happens at the contract date.

Negative gearing

From the 2027-28 income year, a net rental loss on an established dwelling contracted after 7:30pm AEST on 12 May 2026 is quarantined (s26-155 ITAA 1997, as inserted by Act No. 49 of 2026). We carry it forward for each owner and apply it against later rental profits and the capital gain on sale. Properties contracted earlier, and new dwellings, keep normal negative gearing. Grandfathering for a surviving spouse, co-owner or relationship breakdown (ss26-156 to 26-159, Act No. 71 of 2026) is described on our guides but not modelled, because our calculators assume the same owners throughout. Until the new-dwelling instrument is final, we treat "new" and "off the plan" as new.

Stamp duty, grants and the 5% Deposit Scheme

Transfer duty uses each state's 2026-27 schedule, including owner-occupier rates, first home buyer exemptions and concessions, off-the-plan concessions and foreign purchaser surcharges. Title office transfer and mortgage registration fees are included. First Home Owner Grant amounts, price caps and dates, and the 5% Deposit Scheme price caps, come from each state's revenue office and firsthomebuyers.gov.au. Every schedule, with its source, is on the rates page.

Land tax

Land tax uses each state's current thresholds and rates for individual owners, on the land value you enter or, in the full analysis, an estimate of the land share of the price. Victoria's table includes the COVID debt levy. NSW and Victoria assess land tax on a calendar year; the other states on a financial year. The Northern Territory has no land tax.

Income tax

Resident rates as legislated: 16% bottom rate in 2025-26, 15% in 2026-27 and 14% from 2027-28, plus the low income tax offset, the Medicare levy, the Medicare levy surcharge where there's no private hospital cover, and the Working Australians tax offset from 2027-28. Later years use the latest legislated rates. Each owner's tax is worked out on their own income, with and without their share of the property.

Default assumptions, and why

Every default can be changed. We set them from public data so a first run is realistic:

• Interest rates: the RBA's average new-loan rates plus 0.25%: about 6.45% owner-occupier, 6.55% investor P&I and 6.75% interest-only, with the cash rate at 4.60%.
• Rent: estimated from the price and property type, using recent gross yields. Always replace it with a real appraisal.
• Growth: 5% a year for houses and 4% for units, close to long-run averages. Past growth is no guide to future growth, so test lower figures.
• Inflation: 2.5% a year, the middle of the RBA's target band. Amounts two or more years ahead are also shown in today's dollars at this rate, as ASIC's generic calculator relief requires.
• Running costs: typical council and water rates for the property type, Canstar's national average landlord insurance, and management and letting fees for the state.

How we keep it current

We review every state rate and federal threshold each 1 July, and whenever a state budget, a new instrument or the ATO changes something. Draft rules, such as the apportioning determination and the new-dwelling definition, are labelled as drafts wherever we use them. Changes are logged in the changelog, and saved analyses are recalculated when the engine version changes.

What we don't model

Companies, trusts and SMSFs; foreign residents for income tax; the partial main residence exemption and the 6-year rule; pensioner duty concessions; Help to Buy shared equity; and land tax on holdings other than the property you enter. Where a page touches one of these, it says so.

Who we are

Real Estate Insight is free to use. We don't take commissions from lenders, brokers, developers or agents, and nothing on the site ranks or recommends a financial product. Our content is general information, not financial, tax or legal advice, and we're not a registered tax agent. Found an error? Tell us and we'll fix it and log it.