UK mansion tax implementation challenged as study finds 40% of £1.5m homes unrecorded
UK mansion tax set for April 2028 faces major valuation gaps, with a study showing around 40% of homes valued near £1.5m absent from Land Registry records, raising enforcement and appeals risks.
The UK mansion tax, formally proposed as the Additional Council Tax on High Value Residential Properties, is due to take effect in April 2028 and faces significant practical hurdles, according to a new UK study. The report highlights that roughly 40% of properties with estimated values near £1.5 million do not appear in Land Registry sale records, complicating efforts to identify liable homes and calculate accurate bills under the planned levy.
Scope and rates of the proposed levy
The proposed charge would levy an annual fee of £2,500 on residential properties in England assessed at more than £2 million, with steeper bands for homes valued above £2.5 million, £3.5 million and £5 million.
Government projections estimate the measure could raise approximately £430 million per year once fully implemented, making identification and accurate valuation of properties central to delivering that revenue.
Gaps in Land Registry records and valuation thresholds
Researchers found that many high-value properties lack recent transaction records, limiting the Land Registry’s ability to verify automated valuations.
Approximately 40% of homes with estimated values around £1.5 million were not matched to a recorded sale, meaning the valuation agency will often need to rely on indirect data rather than recent market transactions.
Concentration of liable properties in London and the South East
The burden of the UK mansion tax will be heavily concentrated in London and the South East, which together account for an estimated 85% of properties likely to fall inside the charge.
Zoopla’s May 2026 estimates identify about 183,000 homes valued above £2 million in England, including roughly 125,000 in London and 34,100 in the South East, compared with just a few hundred in many northern regions.
Valuation methods, data shortfalls and energy performance gaps
The valuation agency plans to use an automated valuation model that infers prices from sale data and property attributes, supplemented by professional valuers where necessary.
But experts warn that automated methods can struggle at the top end of the market, where scarcity of comparable sales, renovations not visible from public records and long gaps since the last sale reduce accuracy.
The study notes that the average time since the last recorded sale for properties over £1.5 million is about 11 years, and roughly two-thirds of those homes lack an energy performance certificate, a factor increasingly relevant to market value assessments.
Practical enforcement challenges and anticipated disputes
Property professionals and market analysts say the combination of sparse sale histories and heterogeneous high-end housing creates fertile ground for disputes over valuations.
Industry voices expect a wave of appeals from homeowners contesting automated or provisional assessments, particularly in locations outside London where comparable sales are rare and automated models are less reliable.
Government consultation, valuation safeguards and appeal routes
Ministers and HM Revenue & Customs have opened consultations with the property sector to refine implementation details, including exemption criteria and appeal mechanisms.
Officials say they will draw on multiple evidence sources — including sale data where available and property characteristics — and use professional valuers to check cases flagged by the automated system, though they acknowledge on-the-ground inspections may be needed to resolve some disputes.
Looking ahead, accurate mapping of high-value housing and clear, transparent appeal processes will be critical to the UK mansion tax’s credibility and fairness.
With consultation closing on 14 July 2026, policymakers face a narrow window to address valuation gaps, design robust dispute procedures and build public confidence before the levy’s planned rollout in April 2028.