Research shows data gaps may complicate government mansion tax valuations

Researchers have found that around 40% of English homes worth £1.5 million or more have no sales records held by the Land Registry, making it harder for the government to value properties for its new mansion tax.

The tax, officially called the High Value Council Tax Surcharge, will apply to homes in England worth over £2 million from April 2028. Valuations will be based on property prices as of April 2026. The Valuation Office Agency plans to carry out most assessments using computer-based models rather than visiting properties in person.

Because expensive homes are often unusual, with few similar properties sold nearby, these automated estimates may be inaccurate. Homeowners who disagree with their valuation can hire an independent surveyor registered with RICS to challenge the assessment. Annual charges will range from £2,500 to £7,500.