The £2m “Mansion Tax” Threshold Could Fall to £1.5m. What Should London Homeowners and Buyers Do Now?

The government is reportedly considering lowering the entry point for England’s High Value Council Tax Surcharge from £2m to £1.5m. That is not confirmed policy. It is nevertheless a material new planning issue for buyers and owners whose property decisions sit close to the proposed boundary—particularly in London and the South East.

The Times reported on 19 September that lowering the threshold is a “live discussion” within the Treasury ahead of the 28 October Budget. Its report says no decision has been taken. The Treasury’s public response was that tax decisions are set out at fiscal events rather than through comments on speculation.

The distinction is essential. The confirmed government framework still applies from April 2028 to owners of residential property in England worth £2m or more using 2026 values. The confirmed annual surcharge starts at £2,500 and rises to £7,500 for property worth more than £5m. Until the government announces otherwise, £1.5m remains a reported option rather than the legal or administrative threshold.

The Two Headline Property Estimates Are Not the Same

The Times says moving to £1.5m could bring roughly 271,000 homes into scope using current values, more than double the 134,000 it says were expected to be affected by the £2m policy. Its headline describes nearly 300,000 homes and reports a possible £800m annual yield. Those figures reflect the proposal as described by its sources and commentators.

Tax Policy Associates’ analysis, updated on 19 September, produces a different estimate. Scaling from Office for Budget Responsibility figures, it estimates around 245,000 homes in total at a £1.5m threshold—approximately 160,000 more than its estimate for the £2m threshold. It calculates that about 85% of those additional homes would be in London and the South East.

Neither figure should be presented as a settled government count. Tax Policy Associates is explicit that its work is speculative and uncertain. Its property dataset is designed as a lower-bound estimate, while its OBR-scaled revenue scenarios depend on assumptions about charges, behaviour and administration. The useful conclusion is not whether the final number is 245,000 or 271,000. It is that moving the threshold by £500,000 could expand the affected market substantially and concentrate the impact geographically.

A New £1.5m Band Alone May Not Raise the Headline Revenue

The charging structure matters as much as the threshold. Tax Policy Associates estimates that simply adding a modest band beneath the current £2m entry point would raise relatively little additional net revenue after administration and behavioural effects. Its higher revenue scenarios assume a £2,500 charge at £1.5m and increases to the existing bands.

That does not tell us what the government will do. It shows why a report about the threshold cannot be converted into a reliable personal cost estimate. A £1.8m owner does not yet know whether the property would face a charge, what that charge would be, what reliefs might exist or whether the proposal will survive the Budget process. Owners should not mistake modelling for a tax bill.

Why £1.5m–£2m Property Is Now the Commercially Important Segment

A buyer agreeing £1.8m for a London home under the confirmed framework could reasonably have treated the property as outside the surcharge. The latest report introduces a scenario in which that assumption may prove wrong. For a client comparing two properties either side of £1.5m—or deciding whether to improve a home already close to the possible boundary—the uncertainty becomes part of the wider ownership-cost discussion.

The annual charge itself may not determine affordability for a high-income household. The more significant questions are how a formal tax boundary affects valuation evidence, buyer behaviour, future marketability and the amount of capital the client wants concentrated in one property. Those issues become more important where the home is already carrying a substantial mortgage or is only one part of an international balance sheet.

This advances Willow’s earlier coverage of the valuation process for £2m-plus homes. That article explained why a tax valuation, estate-agent appraisal and mortgage-security valuation may produce different numbers. A possible £1.5m boundary would extend the same valuation conversation to a much larger group of properties.

The Purchase Price Will Be Evidence, Not Necessarily the Final Tax Answer

The government’s current policy uses 2026 property values and a targeted Valuation Office exercise. A recent arm’s-length purchase price would clearly be relevant evidence, but the published valuation framework is not based solely on one transaction. Comparable sales, property characteristics, existing records, model-assisted analysis and professional judgement can all contribute.

That matters around a hard threshold. A property marketed at £1.55m but purchased for £1.49m should not automatically be assumed to sit permanently outside a future £1.5m regime. Equally, an asking price above £1.5m would not by itself establish a statutory valuation. The policy, valuation date and methodology would have to be known.

The mortgage lender will make a separate security assessment. If a buyer agrees £1.8m but the lender values the property at £1.7m, that lower figure may restrict mortgage capacity without resolving the future tax position. The client could therefore face a larger cash contribution at completion and continuing uncertainty over how the property is treated for the surcharge.

The Finance Question Is How Much Capital Should Sit in the Property

A potential £2,500 or similar annual charge does not automatically justify borrowing more. Mortgage interest on additional debt can exceed the surcharge many times over. Nor does it automatically justify paying cash. The useful comparison is the complete balance-sheet outcome: cash committed, mortgage cost, retained liquidity, investment risk, future flexibility and the client’s expected use of the property.

For a £1.8m purchase, one client may prefer a £900,000 mortgage and retain capital for business or investments. Another may use a larger deposit because certainty and lower monthly cost matter more. A third may consider interest-only borrowing because there is a credible repayment strategy and preserving liquidity is a deliberate choice. The reported tax proposal does not identify which answer is correct.

Existing Owners Face a Retain, Refinance or Sell Decision

An owner between £1.5m and £2m may have bought the property decades ago and hold substantial equity but limited income. Another may have a large mortgage approaching refinance. A third may already be considering downsizing. The reported proposal affects those clients differently even if the annual charge were identical.

For someone who wants to remain in the home, the relevant work may be cash-flow planning and a review of existing debt. For someone already planning to move, timing and market conditions may matter more than the surcharge. For someone seeking capital, refinancing could provide liquidity but also increases secured debt and interest. No owner should borrow simply to pay an unconfirmed future tax without considering the cost and long-term consequences.

Older homeowners considering later-life borrowing or downsizing need especially careful coordination. A property can be valuable while monthly income is limited. The government has said a support scheme will accompany the confirmed surcharge, but its detail is still to be consulted upon. Clients should not assume either that support will be available to them or that selling is the only response.

International Owners Should Combine This With the “Dip-In, Dip-Out” Decision

Willow’s recent article on London becoming a “dip-in, dip-out” city for globally mobile families asked whether a client should commit £5m cash to a home used for only part of the year. A lower surcharge threshold adds another ownership cost to that assessment, particularly for a £1.5m–£3m London base.

The answer is still not that an overseas buyer should automatically borrow. Residence, property use, income currency, available assets, private-bank relationships and liquidity objectives need to be assessed together. Mortgage debt also does not normally reduce the value on which a property tax is calculated. The ownership and tax consequences remain matters for the relevant advisers.

What Buyers and Owners Should Do Before 28 October

Do not treat the report as enacted policy. Do not assume a £1.49m purchase price permanently avoids a future charge. Do not restructure ownership or increase borrowing solely to respond to a proposal whose detailed design is unknown.

Instead, identify whether the property is plausibly close to £1.5m, £2m or another existing band; record the client’s intended holding period and use; calculate the confirmed ownership and mortgage costs; and add a clearly labelled scenario for a lower threshold. If that scenario materially changes the decision, the client’s mortgage adviser, tax adviser, solicitor and wealth adviser should address their respective parts before exchange or refinancing.

Flexibility is more useful than a prediction. A buyer who retains an appropriate liquidity reserve, understands the mortgage conditions and avoids relying on one valuation outcome is better placed than somebody whose transaction only works if the Budget leaves the threshold untouched.

Professional Advisers Have a Clear Referral Trigger

Tax advisers and private-client solicitors do not need Willow to interpret the surcharge. The finance referral arises when the client is buying, refinancing, raising capital, retaining a home after moving overseas or considering whether debt and liquidity should be rebalanced. A wealth manager may identify that too much of the balance sheet is concentrated in property; a buying agent may identify a client negotiating close to the proposed threshold.

The useful professional message is measured: £1.5m is not policy, but a funding plan for a property close to that figure should not depend on the assumption that £2m can never change. The mortgage can be structured around scenarios without presenting speculation as fact.

How Willow Private Finance Can Help

Willow can undertake a Prime Property Funding & Holding-Cost Review for a £1.5m-plus purchase, refinance or existing home. We assess the property, borrowing requirement, income, assets, existing debt, desired liquidity, ownership route established by the client’s advisers and expected use of the property.

We can then compare appropriate residential large-loan, specialist and private-bank mortgages, including interest-only where there is a credible repayment strategy. For suitable HNW clients, portfolio-backed borrowing can be considered alongside property debt, with investment risk and advice remaining with the investment adviser.

Willow does not advise on whether the surcharge applies or how a property should be owned. We can work with the client’s tax adviser, solicitor, wealth manager, accountant, valuer or buying agent so the funding plan reflects their conclusions rather than being developed in isolation.