Around 4,000 Putney homes (one in ten) could face the government’s new “mansion tax” from April 2028. Properties over £2 million pay £2,500 to £7,500 annually. You can challenge valuations and defer payment if cash-poor. The uncertainty: exact processes won’t be confirmed until early 2026.
What you need to know right now
The government announced a High Value Council Tax Surcharge starting April 2028. Properties worth over £2 million face annual charges of £2,500 to £7,500.
You can challenge it. The government will consult on appeals in early 2026. Based on current council tax challenges, informal challenges succeed about 40% of the time. Formal tribunal appeals drop to 9% success, but most cases resolve before that stage.
If you can’t afford annual payments, deferral until sale or death will be available, although we don’t know what the rules around that will be.
If you are thinking about challenging a decision on your home when it comes, start documenting evidence now: comparable sales, value-reducing factors, measurements. You’re building a case file for 2026-2027.
Don’t panic, but don’t ignore this. Preparation costs nothing and could save £2,500 or more annually.
What we know for certain
The November 2025 Budget confirmed the High Value Council Tax Surcharge:
| Property value | Annual surcharge |
|---|---|
| £2.0m – £2.5m | £2,500 |
| £2.5m – £3.5m | £3,500 |
| £3.5m – £5.0m | £5,000 |
| Over £5.0m | £7,500 |
The surcharge starts April 2028 based on 2026 property values (not 1991 values used for standard council tax). The official government body that decides on your house’s value – the Valuation Office Agency (VOA) – conducts assessments, with revaluations every five years. Charges rise with inflation from 2029-30. Property owners are liable for payment, not tenants, in rented properties. Social housing is excluded.
The Chancellor confirmed the government “will consult on options for support or deferral.” The OBR report states it “assumes there will be a deferral scheme for those unable to pay immediately.” Asset-rich but cash-poor homeowners may defer payment until sale or death – with the surcharge effectively acting as an additional Inheritance Tax. Exact mechanisms await the early 2026 consultation.
What remains unclear though is the appeals process, whether you can challenge before April 2028, VOA response times, evidence requirements, and deferral scheme details.
Which Putney homes are affected
About 4,000 SW15 properties face the surcharge. Detached homes in Putney average £2.19 million, placing most of them automatically in scope.
Priory Lane leads exposure at £6.93 million average. Other high-concentration streets include Heathview Gardens, Roedean Crescent, Roehampton Gate, Bank Lane and Deodar Road. Large family homes between Putney High Street and the Common face substantial risk.
This isn’t just obvious “mansions.” Many affected properties are Victorian terraces or larger flats bought when prices were lower. Your £850,000 purchase in 2010 could now be valued at £2.2 million. Properties worth £1.8m to £2.2m face particular uncertainty – small valuation differences translate directly into £2,500 annual charges.
How challenges probably work (based on existing system)
The final mansion tax appeals process isn’t confirmed, but the existing council tax challenge system provides the likely model.
The current system offers two routes. Formal proposals give you a legal right to challenge if you’ve paid council tax less than six months, if the VOA changed your band within six months, or if your property changed through demolition, conversion, or major structural work. These can be appealed to tribunal if rejected.
Informal band reviews work differently. If you’ve paid council tax over six months and think your band is wrong, you can request a review. The VOA only accepts these with strong evidence, and you cannot appeal to tribunal if rejected. For mansion tax, it’s unclear which route applies, though some version of both seems likely.
The process follows a predictable pattern. Submit evidence to the VOA showing overvaluation. The VOA takes up to six months for formal proposals, 12 months for informal reviews.
If the VOA rejects your formal proposal, you can appeal to the Valuation Tribunal within three months. The tribunal is designed for ordinary people: free, no legal representation needed, written evidence submitted before a 30-60 minute remote video hearing. Written decision arrives within one month. Appeal to final decision typically takes nine months.
One risk: tribunals can increase valuations if evidence shows undervaluation. Rare but genuine.
What evidence works
The VOA accepts specific evidence types and ignores others.
Strong evidence centres on comparable properties: up to five similar properties worth less than yours, with documented sale prices from the Land Registry. Precise measurements matter (VOA measures externally). Value-reducing factors include busy roads, structural issues, no parking, or conservation restrictions.
Comparables only work if they match on four criteria.
- Location: same street or estate in urban areas.
- Type: houses with houses, flats with flats, semi-detached with semi-detached.
- Age: same building period – Victorian with Victorian, not new builds or pre-1900.
- Size: within 10% of your square footage.
The VOA routinely rejects certain evidence. Online price calculators (Zoopla, Rightmove) carry no weight. House price indices are too broad. More than five comparable properties wastes time – only the first five count. Properties outside valid location ranges or of different types get ignored.
Success rates realistically
The statistics reveal where effort pays off. Informal reviews achieve value reductions 41% of the time. The VOA reviews evidence and often adjusts without formal proceedings – the sweet spot for most challenges.
Formal proposals at VOA stage: 43% achieve reductions, 46% unchanged, 4% deleted entirely. At tribunal, success plummets to 9%. By this stage, the VOA has defended its position twice, making reversals uncommon.
Key takeaway: strong initial evidence matters more than persistence. Solid comparable property data often resolves informally. Weak cases rarely improve at tribunal.
How the VOA values properties
Understanding VOA methodology helps build effective challenges. The VOA uses three evidence types in strict hierarchy.
Sales evidence sits at the top. Actual sale prices of your property or similar properties provide the clearest market value indicator. For current council tax, this means 1989-1993 sales in England. For mansion tax, likely 2024-2026 sales around the valuation date.
Without sales evidence, the VOA uses banding evidence. Since all properties are valued at the same date, council tax bands already allocated to similar neighboring properties create patterns. If identical houses on your street sit in lower bands, that strengthens your case.
Settlement evidence carries special weight. Properties where bands changed after challenges prove more persuasive than unchallenged bands, especially tribunal decisions. The independent panel reviews all evidence before deciding, making these determinations credible. The VOA also considers bands settled through agreement, withdrawn challenges, or unchanged after review.
The VOA considers size (measured externally for houses, internally for flats), type and style, age and condition, location and amenities, number of rooms, and layout. What they don’t factor in: improvements after valuation date, current market conditions beyond 2026 snapshot, personal circumstances, or original purchase price.
The improvement indicator trap
If you extend or renovate your property, the VOA adds an “improvement indicator” to your record.
How it works:
- You build an extension or do major renovation
- Building control notifies VOA
- VOA adds an “I” indicator to your property
- Your band doesn’t change… yet
- When you sell, the indicator triggers automatic review
- New owner gets updated valuation
Why this matters for mansion tax: Improvements since 1991 that haven’t triggered a reband (because you haven’t sold) WILL be considered for 2026 mansion tax valuation. Your £1.8m property might become £2.1m once the VOA includes that loft conversion and extension.
What to document right now
You have 12-18 months before VOA conducts mansion tax valuations. Build your evidence file methodically.
Start with comparable properties. Identify three to five similar properties on your street or estate. Check their council tax bands at gov.uk/council-tax-bands. Note “I” improvement indicators – these might be undervalued. Research recent sale prices using Land Registry data from 2023-2025.
Document your property thoroughly. Measure it (external dimensions for houses). Photograph all rooms, gardens, external features. Focus on value-reducing factors: busy road location, properties overlooking yours, structural issues, awkward layouts, restrictive covenants, conservation area limits, limited parking, damp, subsidence.
Review improvement history. List all extensions, loft conversions, major renovations since 1991. Gather building control certificates and planning permissions. Check whether improvements already show as indicators in your council tax record.
Track market context. Follow Putney property sales in your price band. Note local factors like planned developments or transport changes. Save estate agent reports and valuations.
If near £2m (particularly £1.8m-£2.2m), small valuation differences equal £2,500 annually. If your house value tips over into a higher band, it will cost you an additional £1,000-£2,500, depending on the band.
Consider commissioning a RICS Red Book valuation (£250-500+) as of 2026 for professional evidence. Watch 2025-2026 market fluctuations carefully. Note comparable sales just below £2m. Pay attention to neighboring property assessments when valuations begin.
The 2026 consultation: what to watch for
The government will consult on appeals, exemptions, reliefs, and support in early 2026. Critical questions need answers.
Process questions: Will challenges use existing council tax routes or create new systems? Can you challenge before April 2028 or only after assessment? What evidence required? How long for VOA reviews? Will tribunal appeals be available?
Fairness questions: How will properties near £2m be treated? Is there tolerance for measurement margins? What support for asset-rich but cash-poor homeowners? Can payments be deferred until sale?
Practical matters: When exactly will VOA assessments happen? How will you be notified? What deadline for challenges? Any exemptions (e.g., elderly long-term residents)?
The consultation will likely appear on gov.uk.
The deferral option: for those who can’t pay annually
Many Putney homeowners have properties that appreciated over decades, pushing them over £2m, but live on fixed incomes that won’t stretch to £2,500-£7,500 annually. The government recognises this.
How deferral likely works: if you meet hardship criteria (undefined), you won’t pay annually. Accumulated charges plus interest (rate unknown) settle when you sell or from your estate after death. This prevents forcing elderly homeowners to sell decades-long homes to pay the tax.
Crucial unknowns: who qualifies, what “hardship” means, what interest rate applies, whether you can switch between paying and deferring. Property analysts predict “many disputes” over qualification criteria, potentially adding significant tribunal workload.
For Putney homeowners, this fundamentally changes the calculation. Long-term residents on fixed incomes with properties now worth £2.1m aren’t necessarily facing immediate £2,500 annual bills. They may defer until they choose to sell or their estate settles accumulated amounts. The consultation determines whether this provides genuine relief or delays the inevitable with added interest.
This matters particularly for properties just over the threshold. A 75-year-old who bought in 1985 for £180,000 and now owns a £2.1m property might qualify for deferral – very different from a recent buyer who knowingly purchased at £2.2m.
Common questions answered
Q: Can I just not tell the VOA my property’s worth? No. VOA has Land Registry sales data, building control records, and property databases. They’ll assess top council tax bands (F/G/H) automatically.
Q: What if I disagree with their valuation? You’ll be able to challenge it, likely through a process similar to council tax band challenges. Details in 2026 consultation.
Q: Will this affect my ability to sell? Potentially. Properties just over £2m might see reduced buyer interest. Some sellers may negotiate prices below threshold. Market impact unclear until 2027-2028.
Q: Can I appeal before they assess my property? Unknown. Current council tax rules don’t allow preemptive challenges, but mansion tax might differ.
Q: What if property values drop after 2026? Unclear if you can request reassessment between five-year revaluation cycles. Should be clarified in consultation.
Q: Does renovating my property increase my mansion tax risk? Yes. Any improvements before 2026 valuation will be considered, even if they haven’t triggered council tax reband yet.
Q: I’m asset-rich but cash-poor—what support exists? A deferral scheme will be available for those unable to pay immediately. If you meet hardship criteria, accumulated charges plus interest settle when you sell or from your estate. Exact qualification criteria and interest rates determined in early 2026 consultation. See deferral section above for full details.
The bottom line
The mansion tax is coming, but the challenge process isn’t finalised. Based on existing council tax systems, you should be able to contest assessments at no cost.
Your strategy: gather evidence now while you have time. Engage with the 2026 consultation. Understand your property’s realistic market value. Challenge if the VOA overvalues.
For properties near £2m, the difference between £1.95m and £2.05m is £2,500 annually. Worth fighting for, but only with evidence ready. Watch for the early 2026 consultation announcement. We’ll update this guide when appeals procedures are confirmed.
