The New Mansion Tax: What Property Owners Over £2m Need to Know

The Autumn Budget 2025 introduced one of the most significant changes to property taxation in recent years: the High Value Council Tax Surcharge, commonly referred to as the 'mansion tax'. From April 2028, owners of properties worth £2 million or more will face an additional annual charge on top of their existing council tax.

For high-net-worth individuals and property investors, this represents another layer of taxation that must be factored into property ownership decisions. The charges themselves may appear modest relative to property values, but when combined with existing property taxes, the cumulative burden is becoming increasingly significant.

In this blog, we explain how the new surcharge works, who will be affected, and what steps you might consider taking before it comes into force.

What is the High Value Council Tax Surcharge?

The High Value Council Tax Surcharge is a new annual charge announced in the November 2025 Budget, that applies to residential properties valued at £2 million or more. This surcharge will be paid by the property owner, rather than the occupiers or tenants.

The surcharge will be collected through local authorities; however, the funds will be used by the central government (Treasury).

How much will you pay?

The charge will be based on the property’s value:

Property Value	Annual Surcharge
£2m to £2.5m	£2,500
£2.5m to £3.5m	£3,500
£3.5m to £5m	£5,000
Over £5 million	£7,500

Worked example

Alex owns a house in Kensington, London valued at £3.5 million. From April 2028, he will pay: 

• Existing council tax (band H) – assume approximately £2,000 to £3,000

• New surcharge - £5,000

• Total annual property tax – approximately £7,000 to £8,000

Who pays the surcharge and how will properties be valued?

Unlike council tax, the surcharge is payable by the property owner, not the occupier. This has important implications:

• Landlords – pay the surcharge, not the tenants

• Owner-occupies – pay both council tax and the surcharge

• Joint owners – Joint owners are jointly liable for the full amount

• Trusts and companies – The legal owner are liable. Companies may also be subject to ATED.

For landlords, this is a direct hit to profitability. Unlike mortgage interest or maintenance costs, the surcharge provides no tax relief and simply reduces your net rental income and yield.

Valuations

Valuations will be conducted by the government’s Valuation Office Agency (VOA), with taxpayers having the option to challenge and dispute any valuations, an appeals process will be set up accordingly.

The valuation of a property will be based on their open market values as at April 2026. 

The government is consulting on support or deferral options. 

If your property is currently worth close to the £2 million threshold, it's worth monitoring its value as we approach 2026. Properties just below the threshold could be pushed over by market movements, while those just above may benefit from any softening in prices.

Practical Considerations

With over two years before the surcharge comes into effect, there is time to consider your options. Here are some points to think about: 

1. Review your property portfolio

If you own multiple high-value properties, the cumulative impact of the surcharge could be substantial. For example, if you own two properties in London valued at £5m and £2.5m respectively, this amounts to about £10,000 in surcharges alone, without considering council tax, maintenance, insurance and other related rental costs.

2. Consider the rental yield impact 

For landlords of properties affected by these changes, the cost cannot be passed onto tenants, which will directly reduce rental yield. Landlords should consider whether there are better alternative investments and review the impact on their profitability and rental yield of each property.

3. Review cashflow

Consider how the surcharge will be funded on an ongoing basis. For owner-occupiers, this means ensuring sufficient liquidity to meet the annual charge. For landlords, the surcharge must be factored into rental yield calculations – it's a direct cost that cannot be passed to tenants.

The Government has indicated it will consult on deferral options, which may assist asset-rich but cash-poor owners, such as elderly homeowners who lack the income to meet an additional annual charge.

4. Other taxes 

Some property owners may consider whether it makes sense to sell high-value properties to avoid the ongoing surcharge. However, this decision should not be taken lightly as the tax costs of disposal can be significant and may far outweigh the annual surcharge.

For example, a property purchased 20 years ago for £500,000 and now worth £3 million would have an unrealised gain of £2.5 million. On disposal, this could trigger a CGT liability of up to £600,000 (at the current 24% rate for residential property). 

Compared to an annual surcharge of £5,000, it would take 120 years of surcharges to equal the CGT bill on sale.

Remember that the mansion tax sits alongside other property-related costs that already apply:

• Stamp Duty Land Tax 

• Annual Tax on Enveloped Dwellings (ATED) for company-owned properties

• Capital Gains Tax on disposal (up to 24%)

• Inheritance Tax (potentially 40% of the property's value)

For high-value property owners, the total tax burden across acquisition, holding, and disposal is now substantial. Any decision to retain, sell, or restructure property holdings should be made with full consideration of the tax implications at each stage, with the support and advice of a specialist tax advisor. In many cases, the surcharge, while unwelcome, may still be the most cost-effective option compared to triggering a disposal.

Conclusion

The mansion tax represents another layer of taxation for high-value property owners. While the amounts may seem modest compared to the property values involved, they add to the overall cost of ownership, particularly for landlords who cannot pass the charge to tenants.

Need advice on how the mansion tax affects your property portfolio? Contact ASWATAX for a confidential chat.