Financial Adviser Warns New Mansion Tax Could Stall Housing Market Years Before It Begins

Leicester financial adviser Scott Gallacher has warned that the Government’s new mansion tax could “significantly stall” the housing market well before the charge officially starts in 2028 — potentially affecting homes valued from just £1.5 million upwards.

Under the scheme announced in the 2025 Budget, the High Value Council Tax Surcharge will apply to properties worth over £2 million, based on their 2026 valuation. The Government has also stated that affected homes will be re-valued every five years.

Gallacher argues that this structure — a fixed threshold, a two-year delay, and periodic revaluations — is likely to influence behaviour immediately.

“Because the £2m line is fixed and the valuation point is 2026, the impact begins now, not in 2028,” he said.
“Homeowners risk pushing themselves into the tax band simply through normal price inflation or by carrying out renovations before the valuation date.”

According to Gallacher, even households with homes worth £1.5m–£1.8m today could now face difficult decisions, especially in areas of high house-price growth such as London and the South East.

“A perfectly ordinary extension or loft conversion could increase a property’s 2026 value enough to trigger the annual charge,” he explained.
“We could see homeowners delaying work en masse purely to avoid inflating their valuation at the wrong moment.”

He also warned of a potential “stop-start pattern” in renovation activity, as homeowners and developers react cautiously in the run-up to each future revaluation.

Source: - https://rowleyturton.com/why-the-new-mansion-tax-will-hit-the-market-long-before-2028/

Questions Now Being Raised for Property Experts and Economists

Gallacher’s comments raise several questions that housing-market analysts, economists, and policymakers may now need to address:

1. Will the Government uprate the £2m threshold for inflation before 2026?

2. How significant could the slowdown in renovation and development activity be?

3. Will the five-year revaluation cycle produce repeated periods of caution?

4. Could price distortions emerge around the £2m mark?

5. Does the policy risk capturing homeowners never intended to be taxed?