Mansion tax: who decides what your home is worth, and what does it mean for your next move?

The government’s planned High Value Council Tax Surcharge will apply from April 2028 to owners of residential properties in England valued at £2 million or more, using 2026 property values.  It will be an annual charge alongside existing council tax. It is therefore something for potentially affected households to understand and budget for, rather than an additional purchase tax payable simply because they move home.

There has been speculation that the threshold could fall to £1.5 million. Recent reporting says that proposal has been rejected, leaving the planned £2 million entry point in place. However, reports about government discussions should be distinguished from formal policy announcements. Buyers and sellers should work from the published position while remaining alert to any confirmed changes, rather than treating every suggested measure as settled policy.

One of the most useful questions is also one of the least understood: who decides whether a property reaches the threshold? Under the published approach, that responsibility will sit with HMRC’s Valuation Office. They will assess properties using comparable sales and information about their characteristics, supported by valuation models and professional judgement.  An estate agent’s asking price or an owner’s opinion would not determine the tax band.

Completed sale prices would still matter. They provide evidence of what buyers have paid, but an individual transaction would not automatically settle a property’s assessment. The House of Commons Library explains that the official valuation could be higher or lower than the price achieved. Consequently, agreeing a purchase below £2 million would not, by itself, guarantee that the property falls outside the surcharge. Equally, an ambitious asking price would not automatically establish liability.

This distinction matters when discussing marketing strategy.  An asking price is part of the process of attracting buyers and testing demand. The eventual sale price reflects the negotiation between particular parties at a particular time. A tax assessment serves a different purpose. Sellers should therefore avoid choosing a marketing figure solely in the belief that it will determine their future tax position, while buyers should avoid assuming that a negotiated discount guarantees a particular outcome.

Existing council tax bands would not decide eligibility either. The government has explicitly stated that the surcharge would involve a separate valuation exercise, without reference to the current bands based on 1991 values. A home being in Band G or Band H would not, on its own, mean that the surcharge applies. Its existing council tax band would continue separately.

For properties that qualify, the published annual charges begin at £2,500 in the lowest band, rising through £3,500 and £5,000 to £7,500 in the highest band. The lowest charge is equivalent to approximately £208 a month, before any subsequent uprating. That is a meaningful household expense, but understanding its scale allows a more useful discussion than an undefined fear about a “mansion tax”.

For a buyer, the sensible exercise is to consider the full cost of ownership. Mortgage payments, council tax, insurance, maintenance and any applicable surcharge belong in the same budget. The decision should also reflect what the property provides: its accommodation, location, garden, access to schools or transport, and suitability for the years ahead. An additional cost deserves proper consideration, but it is one part of a much wider decision about where and how to live.

For sellers, the practical implication is to prepare for informed questions. A buyer considering a potentially affected home may want to understand the available information before committing. Clear communication can help prevent uncertainty becoming an avoidable obstacle. Relevant documents and accurate property details are useful foundations for that conversation. Where a question concerns formal liability, the answer must come from the official assessment and appropriate professional advice, rather than an assurance given during a viewing.

Homeowners would also have routes to question an assessment. The published consultation proposes a draft list in late 2027, allowing factual inaccuracies to be raised before final banding. It also sets out challenge and appeal arrangements. The proposed framework includes general revaluations every five years, with the next scheduled for 2033. These are features of the published plans, whose final implementation details should continue to be checked.

Could the surcharge influence the housing market? Our assessment is that additional ownership costs could affect some buyers’ budgets and negotiations, particularly around a band boundary. However, a precise price effect cannot responsibly be promised. Properties differ, buyers have different resources and priorities, and local supply matters. A national policy headline cannot tell a homeowner exactly what their individual property will achieve.

For people buying and selling together, it is especially useful to look at the whole transaction. The price achieved on the existing home, the cost of the next property, borrowing requirements and ongoing expenses all interact. Focusing on one figure in isolation can obscure whether the overall move remains affordable and worthwhile.

There is therefore no single answer to whether someone should move before the surcharge begins, wait, or reconsider a particular property. That decision needs to reflect personal circumstances and verified information. A move prompted by family needs, work or a desire to downsize should be assessed on its own merits, with potential tax costs included realistically.

At Langford Rae Property Agents, we have helped local homeowners move since 1986. Our role is to combine that experience and local market knowledge with clear explanations of the issues affecting a sale or purchase. For anyone considering a move around Orpington, Chelsfield or the surrounding villages, preparation and perspective remain valuable: understand the published plans, establish what is relevant to your property, and make decisions with the full picture in view.

Information checked on 15 October 2026. This article explains published plans and reported developments; individual tax liability and final implementation details require confirmation.