The Real Budget Risk for Prime London Sellers Isn't the Mansion Tax

Every prime London owner has heard about the mansion tax by now. The High Value Council Tax Surcharge on homes worth £2 million or more takes effect from April 2028, and it has dominated the conversation among our clients since it was confirmed. But with Chancellor John Healey now confirmed to deliver the Autumn Budget on Wednesday 28 October 2026, the mansion tax may not be the change that matters most to anyone actively weighing up a sale this year.

The bigger question is capital gains tax — and whether it is about to be pulled into much closer alignment with income tax.

A Budget Date Is Set — And a New Chancellor With It

This is the first Budget delivered under Prime Minister Andy Burnham’s government, and the earliest Budget date the UK has seen since 2021. Healey has been clear that the Budget will be built on “fiscal discipline” while giving “businesses and families some of the stability they need to plan for the future.” Stamp duty and council tax are, for now, off the table — Burnham has explicitly ruled out replacing them with a single annual property tax this year, ending months of speculation.

Capital gains tax has had no such reassurance.

The Real Speculation: Aligning CGT With Income Tax

Burnham has said publicly that he wants to look “in detail” at aligning capital gains tax rates with income tax rates — a comment he first made at his Makerfield by-election campaign launch and has not walked back since. This is not confirmed policy. But it is, in the words of tax advisers tracking the Budget, one of the most credible areas of speculation on the table, and a genuine departure from decades of UK tax practice that has consistently made it more efficient to realise value as a capital gain than as income.

What “Alignment” Could Actually Mean for a Prime Sale

For an owner selling an investment property, a second home, or a portfolio asset in prime London, the gap between current CGT rates and income tax rates is not trivial. Full alignment would be a significant change to the arithmetic of any sale — and unlike the mansion tax, which is a known, dated, and calculable annual charge, a CGT change would affect the one-off number on completion day.

We are not in the business of encouraging clients to make decisions on speculation alone, and neither should you. But if a sale or a portfolio restructure was already on your mind for 2027, the sensible move is to have that conversation with your accountant and your broker before 28 October, not after.

Why the Mansion Tax Isn’t the Story for Sellers

The mansion tax is real, it is legislated, and it takes effect from April 2028 with charges of £2,500 to £7,500 a year depending on value — some reports suggest the £2 million threshold could even be lowered to £1.5 million, though the Government has not confirmed this. But it is a holding cost, not a transaction cost. It changes the maths of keeping a property. It does not change the maths of selling one. For owners who are already leaning toward a sale, it is the CGT conversation, not the council tax conversation, that deserves the attention this autumn.

What This Means If You’re Weighing Up a Sale — or a Portfolio Exit

We are already having this conversation with clients across prime and super-prime London. None of it is about panic-selling ahead of a Budget that may change nothing. It is about making sure that if a sale was coming in the next 12–18 months anyway, the timing decision is made with full information rather than caught out by a rate change nobody saw coming.

HMO and Portfolio Landlords Face the Same Timing Question

This isn’t only a super-prime conversation. HMO landlords and portfolio investors face exactly the same arithmetic, often on a larger scale across multiple units. Licensing costs have already risen sharply this year, and for many landlords the question of whether to exit now, restructure, or hold has become considerably more pressing. If you are weighing up the sale of an HMO or a wider portfolio, we would rather have that conversation with you now, on your terms and in confidence, than have the Budget make the decision for you.

The Off-Market Option: Moving Without the Noise

For owners who decide the sensible move is to act before the picture changes, a public listing is rarely the right route. It invites speculation, price anchoring, and a slower process at exactly the point when certainty matters most. An off-market sale, handled discreetly and directly, gives you control over timing that a portal listing simply cannot.

I’ve spent more than forty years in this market, through more Budgets and more speculation cycles than I can count. The clients who do best are never the ones who react to headlines — they’re the ones who get proper advice early and act on facts, not noise. I don’t make excuses. I make results.

If you would like a confidential conversation about your position ahead of 28 October — whether that’s a single prime asset, an HMO, or a wider portfolio — get in touch directly.