Windfall Gains Tax Calculator Australia

What the windfall gains tax calculator does

Windfall gains tax is the Victorian charge on the value a rezoning adds to land, and this calculator estimates it from two numbers: what the land was worth before the amendment and what it is worth after. It subtracts any excluded uplift, decides which band the remainder falls into, and applies that band's rate in the way the band requires.

It also answers the questions that follow the headline figure. How much of the uplift do you actually keep? What is the effective rate once the threshold is taken into account? On a subdivision, what does the tax work out to per lot? And if you defer the liability to settlement, what does the interest add?

A Victorian tax, and only a Victorian one

There is no national windfall gains tax in Australia. This is a state tax created by Victorian legislation and administered by the State Revenue Office of Victoria, and it applies only to land in Victoria rezoned by an amendment to a Victorian planning scheme. New South Wales, Queensland, Western Australia, South Australia, Tasmania and the territories have infrastructure contribution schemes and developer charges of various kinds, but none of them levies a tax on rezoning uplift in this form.

That matters for anyone comparing sites across state lines. A parcel on the Victorian side of the border can carry a liability of half its rezoning uplift, while a comparable parcel elsewhere carries none. The tax is a genuine input into a site acquisition decision, not an afterthought at settlement.

How the bands work

The schedule has three zones, and the middle one is the part people misread.

Uplift at or below the exemption threshold produces no liability. Nothing is payable, and nothing has to be deferred. Between the threshold and the upper band boundary, the rate applies only to the excess over the threshold, so a small amount of uplift produces a small bill and the effective rate rises slowly from zero. At or above the upper boundary, the rate applies to the whole uplift including the first slice, but at a lower percentage.

The design is continuous, not cliff-edged. At the boundary the two calculations produce the same answer, which is why the schedule is written this way. Above the boundary, the effective rate and the band rate are the same number, so every extra dollar of uplift is taxed at that flat rate.

The calculator reports both the band rate applied and the effective rate on the whole uplift, and the gap between the two is the value of the threshold to you. In the lower band that gap can be substantial. In the upper band it closes to nothing unless part of the uplift has been excluded.

Exclusions and exemptions

Not every rezoning is caught, and not every owner pays on the full uplift.

• Rezonings to or from the urban growth zone inside the urban growth boundary are excluded, because that land is already caught by the growth areas infrastructure contribution.
• Rezonings to a public land zone, and rezonings that correct an obvious anomaly in the planning scheme, are excluded.
• Residential land with residential improvements is exempt up to two hectares, applied once per owner per rezoning event.
• Land owned by a charity and used for charitable purposes for 15 years after the rezoning is exempt, though the exemption can be clawed back if that use stops.
• Contracts of sale and options entered into before the tax commenced can be excluded under the transitional rules.

The calculator gives you a single excluded uplift field rather than trying to model each of these tests, because most of them are qualitative and several depend on facts only the owner knows. Put the exempt portion of the uplift in that field and the tax is worked out on what is left.

Deferring the liability

An assessment arrives when the rezoning takes effect, which is often years before any money changes hands. Victoria allows you to elect to defer payment until the next dutiable transaction or relevant acquisition, or for up to 30 years, whichever comes first. Interest runs on the deferred amount for the whole time.

Deferral is therefore a borrowing decision. If your cost of capital is above the interest rate charged, deferring is rational. If it is below, or if the rezoning may not be followed by a sale for a decade, deferral quietly compounds into a much larger number. The calculator lets you enter the interest rate and the years and shows both the deferred liability and the interest cost separately, so the comparison is explicit.

One practical point: the liability attaches to the land. A buyer taking land with a deferred liability needs to know it is there, and the amount usually comes out of the sale price one way or another.

Reading the results per lot

Where the rezoning precedes a subdivision, the tax per lot figure is the number that matters for a feasibility model. Windfall gains tax is assessed on the land as a whole at the time of the rezoning, not lot by lot at the time of sale, so the whole liability has to be recovered across however many lots the site eventually produces. Dividing the tax by the lot count gives the per lot burden to add to your development costs before any margin is calculated.

If the site is held jointly, the ownership share field pro-rates your part of the liability. Owners are generally jointly and severally liable for the assessment, so a share figure describes how the cost is split between you, not a cap on what the State Revenue Office can pursue.

This tool gives an estimate to help you plan and is not legal, financial or tax advice. The Valuer-General's before and after valuations decide the actual liability. Check the current threshold, rates and exemptions with the State Revenue Office of Victoria and take professional advice before acting on the result.

About This Tool: Windfall Gains Tax

Windfall gains tax: use this tool to get an instant, accurate estimate. The figures follow official guidance and every rate and threshold is kept up to date for 2026. Adjust the inputs above to match your situation, or browse all our calculators to plan your next step.