Evidence-led algorithms

The 'Mansion Tax' is coming, and homeowners will soon be asked to respond to banding outcomes created from national datasets and a mass-appraisal process. Mansion Tax Checker aims to help you determine if those outcomes are justified against your property's individual contexts.

We built this website because the new surcharge will raise many questions. There will always be edge cases: homes that straddle band thresholds, are in relative disrepair, or should arguably sit outside the Tax altogether. We also think local trends should matter. Price growth across England has recently been subdued and uneven, with falls in some areas during 2026.

National datasets cannot capture every property-specific nuance, so we built the Valuation Evidence Engine to bring together completed sales, verified property facts, local market movement and condition in a structured chain, creating what we believe is a more individualised and balanced appraisal of your home for these purposes. Crucially, the Engine starts with the same Land Registry base data that the Valuation Office will likely employ.

Under the current proposal, bands will be based on 2026 values until 2033, so an error could affect your tax liability for several years. Mansion Tax Checker helps homeowners test the evidence before that happens, and preserve a balanced record of the data supporting their property's value range under 2026 market conditions.