How to Stress-Test Your Wealth Plan Against Future Tax Changes

Nobody can predict exactly which taxes will change over a 20- or 30-year planning horizon. Capital Gains Tax rates have shifted significantly in recent years, and the possibility of an annual wealth tax is regularly debated in policy circles. Rather than guessing what will happen, the prudent approach is to stress-test your plan against a range of scenarios — so you can see which outcomes your financial position can absorb and which ones require action.

Why CGT Regime Changes Matter to Long-Term Plans

Capital Gains Tax is often overlooked during the accumulation phase of a financial plan, but it can become a significant cost at the point of disposal. If you hold buy-to-let property, additional homes, or shares in a private company, a shift in CGT rates could materially change the net proceeds of a future sale.

The UK's residential property CGT higher rate moved from 28% to 24% in October 2024. Before that it had been 28% for years. Looking further back, the additional-rate CGT band was only introduced in 2016. These are not once-in-a-generation events — they happen regularly, often with limited notice.

Our financial planning tools include a CGT regime-change scenario that lets you apply a custom flat rate, or align CGT to your estimated income tax rate, across all your projected property and business asset disposals. The result is a like-for-like comparison against your baseline plan, giving you a clear view of the net-worth impact at each age.

How a Flat-Rate CGT Scenario Works

The flat-rate CGT scenario replaces the statutory residential, additional-home, and share-disposal CGT rates with a single rate you choose. You can set it anywhere from 10% to 45%.

For example, if you own a BTL property you plan to sell at age 65 and want to model the effect of a 30% CGT rate instead of the current 24%, the scenario projects the additional tax cost year by year and shows the revised net-worth trajectory alongside your baseline. Business Asset Disposal Relief (BADR) rates are intentionally left unchanged — that relief is a separate policy with its own lifetime limit and is not part of the general CGT regime.

The “align to income tax” mode takes a different approach: it estimates your marginal income tax band for each year and applies the corresponding income tax rate as your CGT rate. This is the scenario that would apply if a future government chose to remove the preferential CGT treatment of capital gains entirely and simply taxed them as income — a policy option that surfaces regularly in Budget commentary.

Understanding a Hypothetical Wealth Tax

The UK has no annual wealth tax, and there is no firm government proposal to introduce one. However, the Wealth Tax Commission published detailed research in 2020, and the idea is periodically revived in public debate. For high-net-worth households, ignoring the concept entirely in long-term planning may be overly optimistic.

A wealth tax is fundamentally different from CGT. Rather than applying at the point of disposal, it applies each year on the value of assets above a threshold — whether or not you have sold anything. A 1% annual tax on wealth above £2 million would, for example, cost someone with £3 million in assets £10,000 every year, rising as asset values grow.

Because the levy recurs annually, even a low rate compounds materially over time. Our projection tools model this correctly — the levy reduces your liquid asset pool each year, which in turn reduces future investment returns on those assets, producing a compounding drag that a one-off tax estimate would understate.

Which Assets Count? Scope Matters

One of the most important and contested questions in any wealth tax design is scope: which assets count towards the taxable base? Different proposals have drawn the line in different places.

• Financial assets (cash, ISAs, GIA investments) — almost always included in academic proposals.
• Business assets — often included, though some proposals offered reliefs similar to Business Property Relief for IHT.
• Pensions — excluded from most published UK proposals on the grounds that pension wealth is already locked away and earmarked for retirement income.
• Primary residence — highly contested; most UK proposals excluded the main home or offered a separate, higher threshold for property.

The wealth tax sensitivity scenario in our planning tools lets you toggle each of these scope options independently. Running the scenario with pensions included versus excluded, for instance, will show you how much of your sensitivity is concentrated in your pension pot versus liquid assets — a genuinely useful insight for decisions about where to hold wealth.

How to Use These Scenarios in Practice

The goal of a stress-test is not to predict the future but to understand your plan’s resilience. Here is a practical workflow:

1. Run your baseline plan first so you have a clear view of your current projected net worth and income at each age.
2. Apply the CGT regime-change scenario with a flat rate 8–10 percentage points above the current rate. Note which disposals are most exposed and at what age the cost is largest.
3. Apply the wealth tax scenario with a threshold of £2 million and a rate of 1%. Toggle pensions and the primary residence in and out to identify your most material exposures.
4. Review the delta — specifically the difference in projected net worth at your target retirement age and at life expectancy. A resilient plan remains on track under both scenarios; a fragile plan may require adjustments to asset location, disposal timing, or spending.

If the scenarios reveal meaningful vulnerability, it is worth discussing the results with a regulated financial adviser who can help translate the analysis into specific actions — whether that is repositioning assets into more tax-efficient wrappers, adjusting disposal timing, or simply building a larger liquidity buffer.

What These Scenarios Cannot Tell You

Scenario planning is a tool for improving decisions under uncertainty — not a prediction. A CGT or wealth tax scenario that shows a £150,000 reduction in net worth by age 75 does not mean that outcome will occur; it means your plan is exposed to that amount of risk if that particular policy change happens.

Tax policy is also political, and real changes are rarely implemented exactly as modelled in academic proposals. Transitional reliefs, grandfathering rules, and thresholds that adjust over time can all soften the impact. The scenarios deliberately apply the change cleanly and consistently so that the output is comparable and interpretable — real-world outcomes would likely be more nuanced.

For detailed estate planning, CGT optimisation, and tax-wrapper strategy, professional advice remains important. These projection tools are designed to inform that conversation, not replace it.