Residential Conveyancing Solicitor Natalie Clarke looks at what a potential ‘mansion tax’ could mean for homeowners with high-value properties, and how to start preparing ahead of the Autumn Budget.

What Homeowners Should Know…

There has been widespread speculation in recent weeks that the Chancellor, Rachel Reeves, may look to introduce new taxation measures on high-value properties in the Autumn Budget. Reports suggest that one option under consideration is ending the long-standing capital gains tax exemption on primary residences worth above a certain threshold, potentially around £1.5 million.

This proposal, often referred to as a “mansion tax,” could affect thousands of homeowners across the UK and may have significant implications for the housing market, particularly in areas where property prices have risen sharply in recent decades. While nothing has yet been confirmed, now is a good time to understand what this could mean for property owners.

How Capital Gains Tax Rules Currently Apply to Main Residences

At present, when you sell your main home, any profit you make is generally exempt from capital gains tax thanks to Private Residence Relief. This relief applies provided that the property has been your only or main residence throughout your ownership and you meet certain qualifying conditions.

This exemption is one of the key features of UK property tax law, and it distinguishes main homes from second homes, buy-to-let properties and other investments, which are all subject to capital gains tax on disposal.

Proposed Changes to Capital Gains Tax and High-Value Homes

According to media reports, the Treasury is exploring whether to limit or remove Private Residence Relief for properties above a certain value. If a £1.5 million threshold were introduced:

• Basic-rate taxpayers could face capital gains tax at 18% on any profit above that value.
• Higher-rate taxpayers could face a 24% tax charge on gains.

For example, a homeowner who bought their property decades ago for £300,000 and sells today for £1.8 million could face a capital gains tax bill on £300,000 of profit (the gain above the threshold). Depending on their tax band, this could result in a significant liability.

Which Homeowners Could be Impacted by a Mansion Tax?

• Long-term owners in high-value areas: While London and the South East remain the most obvious regions affected, property hotspots elsewhere, such as parts of the South West, Cheshire, Edinburgh and other popular cities, have also seen prices rise above £1.5 million.
• Older homeowners looking to downsize: Those selling large family homes to move into smaller properties could find themselves unexpectedly liable for capital gains tax.
• Inherited properties: Families inheriting high-value homes may also be impacted, adding complexity alongside inheritance tax planning.

How a Mansion Tax Could Affect the UK Housing Market

Introducing a new tax on high-value homes would not only affect individual homeowners but could also shape wider market behaviour. Property experts warn that such a change might alter how buyers and sellers approach transactions at the top end of the market.

• It could create a “cliff edge” effect around the chosen threshold, with buyers and sellers adjusting behaviour to avoid crossing it.
• It may discourage people from selling their homes, particularly those who have no pressing need to move, reducing the availability of properties in some areas.
• It could lead to a slowdown in property transactions at the higher end of the market across the UK, not just in London and the South East.

House prices in the UK have grown significantly over the last two decades, with some regions seeing sharper increases than others. According to the ONS UK House Price Index, the average house price in England is now over £300,000, while in London it exceeds £500,000. In areas such as the South West, parts of the North West, and Scotland’s cities, long-term growth has also pushed certain properties into higher-value brackets. These regional variations mean the impact of any proposed mansion tax would not be limited to traditional hotspots but could be felt more widely across the country.

At the same time, any change may drive increased demand for professional advice on tax planning, particularly for individuals and families whose homes are approaching the proposed threshold.

Steps Homeowners Can Take to Prepare for Potential Tax Changes

As the Autumn Budget approaches, homeowners may want to keep an eye on developments. While nothing is certain yet, it may be helpful to:

• Review the current value of your property to understand if it could fall within any future threshold.
• Seek early advice if you are considering selling a high-value property in the near future.
• Consider wider estate and tax planning strategies to mitigate potential exposure to capital gains tax or inheritance tax.

Talk to Us

To discuss the issues raised in this blog, make an appointment with our Residential Conveyancing Team