The UK's new High-Value Council Tax Surcharge (HVCTS), often dubbed the 'mansion tax', is set to launch in April 2028, targeting residential properties valued at $2 million and above. This surcharge, ranging from $2,500 to $7,500 annually, is expected to affect approximately 100,000 homes and generate $400 million per year. However, a significant challenge lies in the initial valuation process by the Valuation Office, as data on property prices is often incomplete or missing. This lack of transparency makes it difficult to accurately identify eligible properties, unlike countries such as France, which mandate more comprehensive disclosure of transaction values.
Another major obstacle is the opacity surrounding property ownership, particularly for high-value homes held through complex structures like offshore companies and trusts. Research by Tax Policy Associates indicates that about 23% of offshore companies owning property in England and Wales have not disclosed their beneficial owners, with an estimated $190 billion worth of property lacking proper ownership details. This makes it incredibly difficult for local authorities, like Westminster Council, to identify the legal owner responsible for paying the HVCTS, especially since the tax is levied on the owner, not the occupier. A 2025 Freedom of Information request revealed that Companies House, a central government agency, only collected 3% of fines issued to non-compliant overseas entities, suggesting local authorities will face even greater difficulties.
Transparency International highlights several recommendations to address these issues, including closing loopholes for secret ownership, strengthening the Register of Overseas Entities, and ensuring the Land Registry systematically captures and retains property transaction values. They also recommend providing councils clear legal access to ownership information held by other agencies, such as HMRC (for ATED and Non-Resident Landlords Scheme) and MHCLG (for the Private Rented Sector Database). The government plans to consult in 2026 on how the surcharge will operate, including the treatment of complex ownership structures, and the forthcoming Asset Ownership Review in summer 2026 presents an opportunity to strengthen transparency rules. Without these changes, the 'mansion tax' faces significant enforceability and collection challenges, potentially falling short of its intended revenue goals and creating administrative burdens for under-resourced local councils.
