Why does 1 July 2027 matter for CGT valuations? For affected assets held across the transition, the market value immediately before 1 July 2027 can determine how much of a future gain falls under the old CGT rules and how much falls under the new system. Investors may alternatively be able to use the legislated apportionment method.
If you thought the new capital gains tax rules would only matter when you eventually sell an asset, think again.
For anyone who owns an investment property, private business or holds shares in a start-up on July 1, 2027, one of next year’s most important financial jobs will be establishing what that asset was worth when the rules changed. Failing to obtain a credible valuation could cost some investors hundreds of thousands of dollars.
The reason for that is buried in the transitional rules.
From July 1, 2027, the existing 50 per cent capital gains tax discount will be replaced with inflation indexation and a minimum 30 per cent tax on real gains.
Gains made up until June 30 will keep the existing discount while gains made after July 1 will fall under the new rules. That sounds simple, but it requires an asset to be valued at that exact dividing line.
The Albanese government says taxpayers will have two choices when they eventually sell. They can use the asset’s market value on July 1, 2027, or an ATO-specified formula based on its growth rate over the entire holding period. But there’s an enormous hidden trap. Based on the government’s worked examples, the automatic method appears to assume that an asset grew at a constant compound rate between purchase and sale.
That may be administratively convenient, but it bears little resemblance to how property values, start-ups and private businesses actually grow. Those assets can rise quickly during one period and slowly during another. Forcing a smooth growth rate across the entire holding period can shift gains made before July 1, 2027, into the new tax regime.
The result could be a much higher tax bill that’s detached from what actually happened, as the following examples show.
The property investor
Consider an investor who bought an investment property for $1m on July 1, 2022.
Assume the property grows by 12.5 per cent a year for the first five years. By July 1, 2027, it’s worth about $1.8m. Growth then slows significantly and five years later, the investor sells it for $2m.
Under the existing 50 per cent discount, and assuming the owner is on the top marginal tax rate including Medicare, the tax on the $1m capital gain would be approximately $235,000.
Under the new rules, the result depends heavily on the property’s value on July 1, 2027.
If the owner has a credible valuation showing it was worth $1.8m, almost all the growth occurred before the rules changed.
The first $800,000 of growth keeps the 50 per cent discount. The property then grows by only about $200,000 over the following five years. Once inflation indexation is applied, there may be little or no real gain after July 1, 2027. Using Stockspot’s CGT calculator the estimated tax falls to around $188,000. That’s about $47,000 less than under today’s rules.
Now consider what happens if the owner doesn’t have a reliable valuation and instead relies on the automatic method.
Because the property doubled from $1m to $2m over 10 years, the formula assumes a constant annual growth rate. It estimates that the property was worth only about $1.41m on July 1, 2027.
That shifts a large part of the gain into the period after the new rules begin. The estimated tax rises to approximately $285,317.
The difference between the two methods is more than $97,000. Nothing about the property changed – the purchase price and sale price are identical. The only difference is whether the owner can demonstrate what the property was actually worth on July 1, 2027.
The start up
For start-up founders and employees, the consequences could be far worse.
Imagine a founder starts a company with $100,000 of their own savings on July 1, 2022. The company grows rapidly and their shares are worth $2.5m by July 1, 2027. Growth then slows as the business matures and the shares are sold for $5m in 2032.
Assume the shares don’t qualify for the proposed Innovative Business CGT Concession or the existing small business concessions. This could happen because the company has grown beyond the turnover limit, doesn’t satisfy the final innovation test or falls outside one of the concession’s other narrow eligibility rules.
| Estimated tax payable | Investment property | Start-up founder shares |
| Current system 50% discount | $235,000 Baseline | $1.15m Baseline |
| If you get a valuation Credible market valuation at 1 July 2027 | $188,000 $47k less than today | $1.58m $433k more than today |
| If you use the ATO model ATO automatic (smoothed growth) formula | $285,317 $50k more than today | $2.11m $965k more than today |
Under the current 50 per cent discount, the estimated tax would be about $1.15m.
With a credible $2.5m valuation on 1 July 2027, the estimated tax under the new rules would be approximately $1.58m. That’s already about $433,000 more than under today’s rules.
But without a valuation, the automatic method produces an extraordinary result.
It looks at the rise from $100,000 to $5m over 10 years and assumes a constant compound growth rate. On that basis, it estimates that the shares were worth only about $707,000 on July 1, 2027.
That bears no relationship to the company’s actual growth. Yet it pushes an additional $1.8m of value into the period covered by the new tax rules.
The resulting estimated tax bill rises to approximately $2.11m. That’s $965,000 more than under the existing discount. It’s also about $532,000 more than the outcome using the actual July 1, 2027 valuation.
This demonstrates the particular risk for successful businesses that generate most of their value before July 1, 2027 but aren’t sold until years later.
Getting that valuation could be one of the highest returning investments they ever make.
Build value early
Taxpayers won’t be legally required to obtain a valuation precisely on July 1, 2027. The rules allow the value to be determined later when the asset is sold. But trying to reconstruct a historical value five, 10 or 20 years later could be difficult and expensive.
Property owners may struggle to find comparable sales or evidence of the property’s condition at the time. Start-up founders may no longer have access to forecasts, board papers or detailed financial accounts when staff and advisers who understood the business may have moved on. A valuation prepared close to July 1, 2027 will generally have much stronger evidence behind it.
Business and property owners should focus on two things.
First, create as much genuine value as possible before the new rules kick in. Strengthen your revenue, improve margins, secure long-term contracts and reduce risks that could lower the valuation. Value created before July 1, 2027, will retain the existing 50 per cent discount whereas later gains will fall under the new rules.
Second, absolutely everybody who owns an illiquid asset should lock down a qualified valuer as soon as possible. Demand could be enormous as the deadline approaches. Owners should also start preparing the financial records and other evidence needed to support their valuation.
The message is simple: build as much genuine value as you can before July 1, 2027, then make sure you can prove what the asset was worth.
For some Australians, getting either step wrong could be a $500,000 mistake.
See how the new CGT rules could affect you
The way gains are split before and after 1 July 2027 could make a significant difference to your future tax outcome.
This article was originally published as an opinion piece for The Australian – Capital gains tax valuation trap could cost investors $500,000 (24 July 2026).
