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What is the Stockspot CGT calculator?
The Stockspot CGT calculator is an educational tool designed to help Australians estimate how the new capital gains tax changes announced in the 2026 Federal Budget could affect long term after tax investment outcomes.
The calculator focuses specifically on the proposed move from the previous 50% capital gains tax (CGT) discount system to the new inflation indexed CGT framework announced in the Budget, including the proposed minimum effective tax floor of 30% on many capital gains.
It compares the old and new CGT tax systems across a range of investment scenarios including ETFs, shares, investment property and business ownership.
The goal is to help investors better understand how higher capital gains tax may impact long term compounding and wealth creation over time.
Importantly, the calculator is general information only and does not provide personal financial or tax advice. The calculator uses simplified assumptions and should be viewed as an educational modelling tool rather than a prediction of actual future outcomes.
Why did Stockspot build the CGT calculator?
The new CGT changes announced in the 2026 Federal Budget are complex and many Australians are struggling to understand what they may actually mean in practice.
We built the calculator to help investors estimate the potential long term impact of the new rules across different investment scenarios.
One of the biggest issues with higher capital gains tax isn’t just the tax itself. It’s the impact on long term compounding.
Even relatively small increases in annual tax drag can compound significantly over 10, 20 or 30 years.
The calculator is designed to make those long term impacts easier to visualise.
How does the CGT calculator work?
The calculator compares outcomes under:
• the previous 50% CGT discount system
• the new inflation indexed CGT framework announced in the Budget, including the proposed minimum effective tax floor of 30% on many capital gains.
It applies assumptions around:
• investment growth
• inflation
• holding periods
• marginal tax rates
• timing of the new rules
• different investment types and transaction costs.
The calculator also incorporates the Government’s announced transition arrangements where gains accrued before and after 1 July 2027 may be treated differently under the old and new systems.
Does the CGT calculator provide personal tax advice?
No.
The calculator is general information only and does not take into account your personal objectives, financial situation or needs.
The outputs are estimates based on assumptions selected by the user and simplified modelling assumptions around tax rates, inflation, investment returns and holding periods.
Investors should always speak with a qualified accountant or financial adviser before making financial decisions.
What assumptions does the CGT calculator use?
The calculator allows users to adjust a range of assumptions depending on the scenario being modelled.
These include:
• expected investment returns
• inflation
• holding periods
• marginal tax rates
• property growth assumptions
• business sale assumptions
• contribution levels.
The calculator currently assumes the new CGT rules commence from 1 July 2027 and applies the Government’s announced transitional framework, where gains accrued before and after commencement may be treated under different systems.
As draft legislation and Treasury guidance continue to emerge, some assumptions may change over time.
Why are the CGT differences so large over long periods?
The biggest reason is compounding.
Even relatively small increases in tax drag can materially reduce after tax wealth over long investment periods.
The calculator is designed to demonstrate that the impact of higher CGT isn’t just about one year’s tax bill. Over decades, the cumulative effect can become very significant.
That’s particularly true for younger Australians still building wealth over long time horizons.
Does the CGT calculator predict future market returns?
No.
The calculator does not predict future market performance or investment returns.
It simply models hypothetical scenarios using user selected assumptions to estimate the potential impact of the new CGT framework.
Actual investment returns, inflation and tax outcomes will vary significantly over time.
Does the CGT calculator include inflation?
Yes.
Inflation is central to the new indexed CGT framework and is incorporated into the modelling.
Importantly, during periods of relatively low inflation, the new indexed system generally results in materially more tax than the previous 50% CGT discount system.
The calculator allows users to test how different inflation assumptions may affect long term after tax outcomes.
Does the calculator include the negative gearing changes?
No.
The calculator is specifically focused on modelling the impact of the new capital gains tax changes announced in the Budget.
While the Budget also introduced changes to negative gearing, those changes are not currently incorporated into the modelling.
That means property scenarios within the calculator focus only on the CGT impact and do not attempt to estimate financing costs, rental income, deductions or the impact of reduced negative gearing benefits.
Does the calculator include the new trust tax rules?
No.
The calculator focuses specifically on the new CGT framework and does not currently model the separate trust taxation reforms announced in the Budget.
Trust taxation can become highly complex depending on:
• beneficiaries
• business structures
• trust deeds
• distribution strategies
• company beneficiaries
• residency and succession planning arrangements.
As a result, the calculator should not be relied upon for trust structuring or trust taxation decisions.
Why does the calculator show such large impacts for startup founders and business owners?
Startup founders and business owners are particularly exposed because much of their long term financial upside often comes from a single capital gains event when eventually selling a business.
The calculator attempts to demonstrate how replacing the previous 50% CGT discount with the new indexed CGT framework and minimum tax settings may materially reduce the after tax reward from long term entrepreneurial risk taking.
However, actual business sale outcomes vary enormously depending on structure, residency, timing and other concessions that may apply.
Does the CGT calculator account for superannuation?
Not directly.
The calculator primarily focuses on investments held outside superannuation.
Superannuation operates under a separate concessional tax framework and may become relatively more attractive under the new rules.
However, the calculator does not attempt to fully model super contribution strategies, preservation rules or pension phase taxation.
Why can tax outcomes still be higher if capital gains are indexed for inflation?
At first glance, taxing only “real” gains after inflation may sound like it should reduce tax outcomes for investors.
However, the new framework announced in the Budget doesn’t simply replace the previous 50% CGT discount with pure inflation indexation.
The Government has also proposed a minimum effective 30% tax floor on many capital gains.
That distinction matters enormously.
Under the previous system, investors who held assets for more than 12 months generally only paid tax on half of the capital gain, regardless of inflation.
Under the new framework, inflation is used to increase the asset’s cost base before calculating the taxable gain, but the proposed minimum tax floor may still result in materially higher effective tax outcomes in many scenarios.
This is one reason the calculator may show significantly different long term after tax outcomes compared to the previous system.
What role does the proposed 30% minimum tax floor play?
The proposed minimum effective 30% tax floor is one of the most important parts of the new CGT framework.
While inflation indexation reduces the taxable gain by adjusting the asset’s purchase price for inflation, the minimum tax floor effectively limits how much benefit investors receive from that adjustment.
In practice, this means some investors may still face materially higher effective tax rates than under the previous 50% CGT discount system, particularly for long held growth assets.
The interaction between inflation indexation and the proposed minimum tax floor is one of the key drivers of the long term differences shown in the calculator.
Why do lower inflation environments often produce larger differences?
Inflation plays a major role in how the new system operates.
During periods of higher inflation, the indexed cost base rises more quickly, which can reduce the taxable gain.
However, during periods of relatively low inflation, the inflation adjustment becomes much smaller. In those environments, investors may receive far less benefit from indexation while still being subject to the proposed minimum tax floor.
That can result in materially larger tax outcomes compared to the previous 50% CGT discount system.
The calculator allows users to test different inflation assumptions because the long term impact of the reforms can vary significantly depending on future inflation levels, holding periods and investment returns.
Can I rely on the calculator for tax planning?
No.
The calculator is an educational modelling tool only.
It simplifies many aspects of the tax system and cannot account for every investor’s:
• income
• deductions
• carried forward losses
• residency
• structures
• estate planning
• business ownership
• trust arrangements
• offsets and concessions.
Investors should always seek personalised advice from a qualified accountant or financial adviser before making decisions.
Will the CGT change calculator be updated?
Yes.
The changes announced in the Budget still need to pass through the legislative process and implementation details may evolve over time.
Stockspot expects to continue updating the calculator as:
• draft legislation is released
• Treasury guidance becomes clearer
• technical implementation rules are finalised
• consultation processes continue.
Future governments may also amend or reverse aspects of the new tax framework over time, which could result in further updates to the modelling.
How are the Stockspot portfolios affected by the new rules?
The new tax changes may increase the importance of tax efficient investing over time.
Stockspot portfolios are already designed around many of the principles likely to become even more valuable in a higher CGT environment, including:
• low turnover ETF investing
• diversified long term asset allocation
• optional “buy only” rebalancing
• automated tax reporting
• minimising unnecessary realised capital gains where possible.
Unlike many high turnover active funds and unit trusts, Stockspot portfolios are built using diversified ETFs that generally realise fewer taxable events over time. That can help reduce ongoing tax drag and improve after tax outcomes over the long run.
The new transitional CGT framework is also likely to create major administrative complexity for investors manually managing portfolios across multiple brokers and structures.
Stockspot expects to update its tax engine and reporting systems to reflect the final legislation once implementation details are confirmed. That means clients shouldn’t need to manually calculate split tax treatments themselves.
If you’d like to learn more about how Stockspot portfolios are designed to help investors build long term wealth in a tax efficient way, you can get started here.
What’s the most important thing investors should remember?
Don’t panic.
While the new rules may reduce after tax returns over time, the core principles of successful investing remain exactly the same.
Diversification still matters. Discipline still matters. Compounding still matters.
For most investors, staying invested, remaining diversified and continuing to focus on long term goals will still likely matter far more than reacting emotionally to short term political or tax changes.
This calculator is general information only and should not be relied upon as personal financial or tax advice.
