New analysis suggests thousands of second home owners already paying double council tax could also be swept into Rachel Reeves’s proposed mansion tax.

• Hamptons estimates around 4,300 second homes currently charged the second home premium are likely to cross the new threshold.
• The tax will apply after the top three council tax bands (F, G, H) are revalued, targeting the most expensive 300,000 homes in England.
• Based on recent sales, the mansion tax is expected to apply to homes worth £1.4m–£1.5m+.

With more than 200 councils already charging double council tax on second homes – and more planning to follow in 2026 – the number of households exposed to a second levy is set to increase.

Early estimates suggest affected owners could face an average £2,000 annual surcharge, helping the Treasury raise around £600m. In high-value areas like Westminster, some owners could end up paying triple the council tax once the mansion surcharge is added.

The impact will fall unevenly:

• 43% of Band H and 17% of Band G homes are expected to be caught.
• Even some middle-income families with Band F homes valued at £1.5m+ may be affected.
• Meanwhile thousands of Band A–E properties will escape the tax entirely because their bands will not be revalued.

London is expected to be hit hardest, with one in 15 properties likely to fall into scope; in Kensington & Chelsea, the share rises to 45%.

The levy is unlikely to take effect before 2028, allowing time for a nationwide revaluation. A separate proposal for a 1% levy on homes above £2m is also being explored.