The time-apportionment method is the alternative route through the enacted 2027 capital gains tax (CGT) transition — the other way, instead of a market value, of separating gains built up before 1 July 2027 from gains built up after it. It is set by section 112-185 of the amending Act. But as at July 2026 the detailed method had not been published: section 112-185 leaves it to a legislative instrument that had not yet been made, so the market-value method is the route the law currently spells out.

That makes this a short answer with an honest gap in the middle. The default is enacted and stateable; the apportionment alternative is enacted in principle but not yet filled in.

What is the time-apportionment method for transitional CGT?

It is the apportioning alternative to a 30 June 2027 market value. The Treasury Laws Amendment (Tax Reform No. 1) Act 2026 — royal assent 26 June 2026 — applies to CGT events on or after 1 July 2027. A “CGT event” is the trigger that crystallises a capital gain or loss, most commonly the sale of an asset.

For an asset held on 30 June 2027, the enacted law sets up a transition so that each period of ownership is taxed under the rules in force at the time. As at July 2026, the law gives two ways to draw that line:

Method	What it uses to split the gain
Market value (the default)	A value fixed just before 1 July 2027
Apportionment (section 112-185)	A method to be set by legislative instrument

The apportionment route is the “time-apportionment” method the query asks about. Its own section heading describes it as a method for “apportioning capital gains and losses between realisation events and earlier deemed CGT events” — in other words, splitting the gain by reference to the eventual sale and the deemed 1 July 2027 changeover, rather than by reference to a valuation on that date. The exact method, though, is what section 112-185 leaves to a later instrument.

The market-value default it sits alongside

The default is enacted primary law, and it is worth stating clearly because it is the position that operates now. Under sections 112-155, 112-165 and 112-175 (depending on the type of asset), an asset held on 30 June 2027 is treated as sold just before 1 July 2027 at its market value just before that date, and reacquired just after for the same amount. Gains built up before the changeover keep their old treatment; gains from 1 July 2027 fall under the new rules.

Those new rules, in summary and as at July 2026: the enacted reform ends the 50% CGT discount for individuals, trusts and partnerships; brings back CPI indexation of the cost base for most cost base elements; and applies a minimum 30% tax to residential and non-residential capital gains under a new Division 119. The discount is retained for new residential dwellings and qualifying affordable housing, and complying super funds keep the 33.33% discount.

The Act itself frames the choice as using “an apportioning method determined under section 112-185” instead of the market-value default. So the two methods are enacted as options — but only one of them is currently spelled out in enough detail to apply.

How the apportionment method is meant to work

At a general level, an apportionment method splits a gain by time rather than by a valuation. Where a market value draws the line with a single figure at 30 June 2027, an apportioning method would instead work out how much of the whole-of-ownership gain belongs to the period before 1 July 2027 and how much belongs after — by reference to the two CGT events the section names, not by a valuation on the changeover date.

Beyond that general shape, the detail is not something to generalise about, and this guide does not. A market-value split and a time-based split can produce different results for the same property, which is exactly why the law offers a choice — but the direction and size of that difference depend on the method’s finalised rules and on figures no general article can supply. Neither route is presented here as the “right” one.

Because the method is not yet published, even a broad statement of when the apportioning route would suit a holding better than a market value cannot be pinned down yet. That is a question for the finalised rules and a registered tax agent, not for a general guide.

Tax outcomes depend on your circumstances — speak with a registered tax agent before acting.

Why the detailed method is not published yet

Section 112-185 delegates the apportioning method to the Minister: it provides that the Minister “may, by legislative instrument, determine a method” for the apportionment. That is a discretionary power — “may”, not “must” — and as at July 2026 no such instrument had been made. The Federal Register of Legislation showed zero legislative instruments registered under the amending Act (Act No. 49 of 2026). As at July 2026, the detailed apportionment method is not yet knowable — check the Federal Register of Legislation for any later instrument before relying on it.

Two things follow. First, the detailed apportionment method — its formula, and how it would compare with a market value for a given property — is not on the public record, so it is not stated here rather than guessed at. Second, while the instrument is unmade, the market-value default is the route the enacted law fully sets out for the transition.

This can change. The reform is enacted, and the ATO guidance and instruments that fill in the working detail were still pending as at July 2026. Until the section 112-185 instrument is made, the time-apportionment method’s mechanics remain unpublished.

How does this apply to fractional interests like Brix?

The transition above describes how the law treats a CGT asset such as a directly held property. A Brix is a different kind of asset. A Brix is a fractional economic interest in a property — a financial product under Chapter 7 of the Corporations Act 2001 (Cth), not ownership of the property and not a loan — and the owner remains the registered legal owner of the home.

As at July 2026, no ATO guidance and no registered legislative instrument set out how the 2027 transition — including any market-value method or the section 112-185 apportionment method — applies to fractional or indirect interests in residential property. This guide does not fill that gap. How the transition treats a Brix is a question for a registered tax agent and for the Product Disclosure Statement, not something to infer from the rules for directly held property.

Under the MyBrix Product Disclosure Statement current as at July 2026 (version 4.0), each property is divided into 10,000 Brix representing all of its economic benefits — future net sale proceeds and, where applicable, net rental proceeds.

Where the detail will be confirmed

The transition is enacted law; the working detail of the time-apportionment method — the section 112-185 instrument — was still pending as at July 2026. The amending Act and the ATO’s guidance on the reform are the primary sources to watch, and a registered tax agent can confirm how any of it applies to a specific property.

For the CGT basics this builds on, see our guide to how capital gains tax is calculated on property; for the market-value side of the same transition, see our guide to property valuations and the 30 June 2027 rules.