Mansion Tax Valuation: Why A Price Below £2m May Not Be Enough

A price of £1,995,000 may look like a neat answer to the £2 million mansion tax threshold. It does not guarantee the property will escape the charge. The agreed price, the tax valuation and the mortgage lender’s valuation serve different purposes, and they can produce different figures.

The “mansion tax” is the High Value Council Tax Surcharge announced in the November 2025 Budget. It is due to apply from April 2028 to owners of residential property in England valued at £2 million or more in 2026. The details remain subject to government consultation and legislation, and could change.

The threshold is already shaping negotiations. Tax Policy Associates’ September 2026 analysis of Land Registry data found that sales in the £10,000 band immediately below £2 million rose from 0.44 per cent to 2.27 per cent of transactions between £1.7 million and £2.3 million after the announcement, roughly five times their previous share. It found no evidence, so far, of a wider fall in property values.

My concern as a mortgage broker is what buyers assume that negotiation has resolved. A purchase can look carefully negotiated and still leave an unexpected tax charge or a funding gap.

How will properties be valued for mansion tax?

The Valuation Office Agency (VOA) will use comparable sales and the characteristics of each property to assess its value in 2026. An individual sale price is evidence, but it does not automatically determine the property’s band.

A negotiated discount is a definite saving on the purchase price. Any saving on the annual surcharge remains uncertain until the VOA’s assessment is known. I would treat those as separate outcomes when deciding what to offer.

What if the lender’s valuation comes in lower?

For buyers using finance, there is a third figure: the lender’s valuation of the property as security. A mortgage agreed in principle does not remove the risk that this comes in below the purchase price.

Take an illustrative purchase at £1,995,000, with borrowing capped at 60 per cent of the lender’s valuation. If the valuation matches the price, the maximum loan is £1,197,000. If the lender values the property at £1.9 million, it falls to £1,140,000, and the buyer needs another £57,000 in cash before transaction costs. This example is for illustration only; lending criteria and loan-to-value limits vary by lender and borrower.

Before committing, ask what valuation the borrowing assumes and where any additional equity would come from. For buyers whose wealth is held in investments, businesses or other properties, the ability to raise cash on time matters as much as overall net worth.

Could the bigger risk be a slower sale?

So far, the evidence shows prices adjusting around the threshold, not a broader fall in values or transaction volumes. Tax Policy Associates cautions that the data cannot yet measure those wider effects.

There is still a plausible reason to allow for longer selling periods: sellers who resist a reduction may hold out rather than transact. Tax Policy Associates notes that the Office for Budget Responsibility’s modelling already allows for a temporary dip in transactions for this reason. It is a potential response, not a demonstrated one.

For anyone relying on a sale to repay a bridging loan or fund an onward purchase, I would test the achievable price and the completion date separately. If an acceptable offer arrives three months later than expected, how much interest and holding cost accrues, and does the repayment deadline allow for it? A price reduction can be calculated immediately; the cost of waiting builds up and can weaken a seller’s negotiating position.

How much should the annual charge influence a purchase?

Under the announced bands, a property valued between £2 million and £2.5 million would attract a surcharge of £2,500 a year, due to rise annually with CPI inflation. A £25,000 price concession is therefore roughly equivalent to ten years of the initial charge. Equally, a seller who accepts a substantial discount solely to bring the price below £2 million may gain nothing if the VOA still places the property above the threshold.

I would compare the whole transaction before changing course. A lower price, a different property or a revised borrowing structure each affects upfront costs, available cash and ongoing interest. The surcharge is only one part of that calculation, and it belongs in the ownership budget alongside mortgage payments, maintenance and other commitments.

Enness does not provide tax advice. A qualified tax adviser should assess your individual position.

The threshold can influence the price. It cannot settle the value.

Before exchanging contracts, a buyer should understand three things: the cash required if the lender values the property below the purchase price; the ongoing budget if the property falls within a chargeable band; and the consequences if a sale needed to fund the purchase takes longer than expected. Test each separately, because one favourable outcome does not guarantee the others.

The same applies to refinancing. If the proposed loan depends on a particular valuation, establish how a lower figure would affect the amount available, and allow for the time and cost of raising extra cash from investments or a business.

Agreeing £1,995,000 settles what the seller receives. It leaves the lender’s assessment and the tax valuation to be determined separately. The strongest position near a band boundary is a purchase that still works financially if those figures differ.

Mansion tax valuation FAQs

When does mansion tax start?

The High Value Council Tax Surcharge is due to take effect in England from April 2028, based on property values in 2026. The details remain subject to consultation and legislation.

Will buying below £2 million avoid mansion tax?

Not necessarily. The VOA will assess value using comparable sales and property characteristics, so a purchase price below £2 million does not guarantee an assessment below the threshold.

Has mansion tax caused house prices to fall?

Research shows more sales clustering just below £2 million since the announcement, but no evidence so far of a wider fall in property values attributable to the tax.

Will a mortgage valuation determine the mansion tax band?

No. The lender’s valuation assesses the property as security for borrowing; the VOA’s assessment determines the tax band. Neither is guaranteed to match the agreed purchase price.

 

Your home may be repossessed if you do not keep up repayments on your mortgage or any other debt secured on it.

Enness Global is a trading name of Enness Limited, authorised and regulated by the Financial Conduct Authority (FRN 565120). Enness does not provide tax or legal advice. This article reflects announced policy as of October 2026, which may change, and is not a personal recommendation.