A man who bought well is being penalised for it by a formula that cannot see what he did.

He is 47, a facilities manager, and he owns two houses on Brisbane's northside. He bought the first in 2020 for a shade over $500,000. Like a lot of south-east Queensland stock, it did something extraordinary in the years that followed and then stopped. He is not distressed and he is not selling. He had a narrow, technical question, and it is the best question we have been asked in weeks.

"There are two ways to value my property for the new capital gains rules. One costs me nothing. Which one do I use?"

The honest answer is that the free one could cost him about $49,000, and the reason why is the most under-reported thing in this entire reform.

What actually changes, in one paragraph

From 1 July 2027, capital gains on most investments stop attracting the old 50 per cent discount and instead run through an inflation-indexation system with a minimum effective rate of 30 per cent. Anyone still holding an asset on that date does not get one regime or the other. They get both. The rules create a deemed sale on 30 June 2027 — a line ruled through the middle of your ownership. Everything left of the line is taxed under the old discount; everything right of it under the new indexed system.

Which means every investor in the country now needs a number: what was this property worth on that date?

The choice nobody is examining

For listed assets there is no problem. A share, an ETF, a parcel of crypto all have a posted price on 30 June 2027, so the split is arithmetic.

Property has no posted price. So investors get two options.

Option one: pay for a formal valuation. Roughly $500 for a small apartment, $1,500 to $2,000 for a larger house, more for anything commercial or complex.

Option two: use the official apportionment formula — free, and written into the rules. Nine steps, no valuer, no invoice.

Option two looks like a gift. It is being reported as a compliance saving. And for a large number of investors it is the single most expensive decision they will make this decade — because of one assumption buried inside it.

The formula assumes your property grew at a perfectly even rate, every day, for the entire time you owned it.

Why that assumption is so costly

Consider what actually happened. Brisbane, Perth and Adelaide roughly doubled in a compressed handful of years, then flattened. That is not an even growth curve. That is a steep climb followed by a plateau.

The formula cannot see the shape. It sees a start value, an end value and a length of time, and spreads the growth evenly across the whole period. So gains that genuinely occurred years ago — squarely inside the era of the 50 per cent discount — get reassigned by arithmetic into the post-2027 window and taxed at the higher rate.

One senior tax adviser put the mechanics plainly: if growth is uneven, and particularly if most of it happened before 30 June 2027, you are far better off with a formal valuation. One accounting body's tax lead was blunter — a formula split is only fair if it reflects reality, and for anyone whose asset did most of its growing early and then flattened, it does not.

The numbers are not small. On a property bought in 2020 for $500,000 and sold years later for $1.5 million — doubling early, then growing more slowly — a high earner pays roughly $273,000 under the free formula against roughly $224,000 with a valuation. A $49,000 difference, for declining to spend perhaps $1,500.

A second, entirely separate worked example lands in the same place. A $428,000 gain, all of it accrued in the first half of the holding period, still has half of it — $214,000 — pushed into the post-2027 calculation anyway. Extra tax for using the free option: more than $52,600.

The part that should make good investors sit up

Here is the uncomfortable symmetry, and it is why we think this story matters more than a red-tape complaint.

The formula punishes uneven growth. Uneven growth is what good selection produces.

An asset that ground out a flat 4 per cent a year for a decade is barely affected — the even-growth assumption is roughly true for it. The asset bought early on a street that then ran hard is the one the formula misreads most severely. The better the timing and the better the street, the steeper the curve, and the more of your historic gain gets dragged forward into the expensive regime.

So the investors most exposed here are not the careless ones. They are the ones who got it right.

And notice what the tax system is now asking. Not "what is this suburb worth?" It wants a defensible value at one address, on one date, and implicitly the shape of that address's growth curve. A suburb median cannot answer that. We have seen the spread between the best and worst streets inside a single suburb run to 20 to 30 per cent on effective yield, and price trajectories diverge just as sharply — one street re-rating hard while another four hundred metres away goes sideways for years. Averaged at suburb level, both look like the same asset. They never were, and from 30 June 2027 the difference between them is a number on a tax return.

This is the same argument we have made about why one street can add $210,000 and the one behind it adds nothing, only now there is a price attached to it. Data that resolves to the street is not a nicety. It is the evidence base for what your asset actually did.

What he should do, and what you should do

We told him three things.

Get the valuation. On the figures involved, a four-figure fee against a five-figure tax difference is not a close call. The regulator also has more scope to reject a retrospective valuation than a contemporaneous one, so a value struck at the time is worth more than a value reconstructed later.

Book it early. There are fewer than 10,000 registered valuers in Australia and credible estimates that more than five million assets may need valuing. More than two million investors are heading for the same door with the same deadline. Prices rise and availability disappears when demand arrives all at once.

Do not assume the free option is the neutral option. It is a guess about the shape of your growth curve, and you are the one who pays if the guess is wrong. Run both numbers before you choose. As with the sell, hold or buy question so many investors got stuck on this year, the answer is specific to your asset and your income, not to the headline. This is a conversation for a registered tax agent who has actually read the apportionment method.

Consultation on the current draft rules is still open and more detail is yet to be settled, so some of the fine print will move. The deemed-sale date will not.

The wider point

It would be easy to read all of this as another reason to give up on residential property, and that is the wrong conclusion.

Nothing here changes what a property earns, who wants to live in it, or what it will be worth in 2035. It changes the administration of the gain — and it does so in a way that specifically rewards owners who can evidence what their asset really did, street by street, year by year. Investors who bought on data are better placed than investors who bought on a median, because they can prove the curve.

The compliance burden is real and the deadline is fixed. But the asset-selection question is unchanged and, if anything, sharper: with less generous tax treatment on the way, more of your return has to come from the property rather than from the concession. That is the same conclusion we reached when lending conditions tightened for investors this year — fewer purchases means every one of them has to be right. It has always favoured the people doing the work at street level.

A formula can average your growth. It cannot average away the difference between a good street and a bad one — and that difference was decided the day someone chose one over the other.

This article is general information only and does not take your personal circumstances into account. It is not tax, financial or legal advice. Capital gains tax treatment depends on your individual situation and the legislation discussed is still subject to consultation. Speak to a registered tax agent or licensed adviser before acting.