Challenge 
How to record your home's 2026 condition
By Simon Dredzen, active in the prime central London property market for over two decades · Reviewed 8 November 2026
The mansion tax uses each home's value at April 2026, but the draft valuations aren't expected until autumn 2027 and bills until March 2028. By then you may have renovated, repaired or extended. A dated record made now is evidence that is hard to rebuild later.
Why now
If your home had damp, an old kitchen, a roof that needs replacing or other problems in 2026, they are likely to be relevant to its April 2026 value, and dated evidence is what shows they existed then. Once they are fixed, the proof goes with them. The closer your record is to April 2026, the more weight it carries. If anything has changed since April, note what changed and when.
Recording your home now doesn't commit you to anything, and you don't lose the right to challenge later if you don't. It simply makes a future challenge easier to support.
The checklist
- Dated photographs of every room, inside and out, including anything worn, dated or defective. Keep the original files, which hold the date they were taken.
- A measured floor plan. An overstated floor area is a common cause of overvaluation. Note whether any space is a basement, has low ceilings or no natural light.
- Surveys and reports: building surveys, damp or subsidence reports, and quotes for repairs you haven't yet done.
- Your lease (for flats), with recent service charge and ground rent statements and any notices of major works.
- Location drawbacks: photos or notes of a busy road, railway, commercial neighbours, flood risk, or no parking or outside space.
- Sale attempts: offers you received, or a listing that didn't sell at its asking price.
- Nearby sales: completed sales of similar homes around April 2026, ideally in your building or street. HM Land Registry sold prices are free to search.
Keep everything in one folder, with a short note of the date and what each item shows. Under the proposals, the consultation proposed excluding estate agent estimates and property website valuations, and the Valuation Office will publish guidance on the evidence it accepts, so focus on facts and completed sales.
Then check where you stand
Use our free checker to see your home's estimated April 2026 value and how close it is to a threshold. If it's close, a free personalised preview shows what our Evidence Pack would record for your home.
Questions
What date is my home valued at for the mansion tax?
April 2026, under the proposals. The detailed valuation assumptions will be set out in regulations; bills start in April 2028.
What evidence should I keep for a mansion tax challenge?
Dated photographs, a measured floor plan, surveys and repair quotes, your lease and service charge statements for a flat, notes of location drawbacks, and completed sales of similar homes around April 2026.
Do I lose my right to challenge if I don't record my home now?
No. Recording your home's condition now simply makes a future challenge easier to support, especially if you later renovate or repair it.
More guides
- How much is the mansion tax?
- Who pays the mansion tax?
- Mansion tax and leasehold flats
- Mansion tax appeal: how to challenge or appeal your band
- Mansion tax in Chelsea
- Mansion tax in Kensington
Sources: the HM Treasury consultation on the High Value Council Tax Surcharge (closed 14 July 2026), the government's publications on the surcharge, including its response of 28 October 2026, House of Commons Library briefing CBP-10934, and the Finance Bill (Part 3). The Bill sets the bands and who pays; the response confirmed the deferral criteria and exemptions. The valuation date, challenge process, interest rates and other details will follow in the Finance Bill 2026, regulations and guidance, and may change before April 2028. This is general information, not tax, legal or valuation advice.