Data sources
The market-rent comparison uses two publicly available ONS datasets. Both are built from rents the Valuation Office Agency collects from letting agents and landlords, so they reflect rents actually paid rather than asking rents:
- ONS Price Index of Private Rents (PIPR). Monthly rent statistics published by the Office for National Statistics. We use the average rent by bedroom band for each local authority, region and England.
- ONS Private Rental Market in London. Lower quartile, median and upper quartile rents by London postcode district, property type and bedroom count. It's the only district-level series ONS publishes, so quartiles are only available for London. Area statistics are a guide to the local market, not a valuation of your home.
How a single check works
When you enter a postcode, property type and bedroom count, we resolve a comparison in this order:
- Postcode district. We take the first part of the postcode (e.g.
E8,SW2) and look for the ONS Private Rental Market in London quartiles for that district, filtered to your property type and bedroom count (nearest bedroom count if the exact one is suppressed). This is the only district-level series the ONS publishes, so it covers London. - Local authority. Everywhere else we place the district in its local authority using the ONS National Statistics Postcode Lookup (the authority that holds most of the district's live postcodes — the result shows the share) and use the ONS Price Index of Private Rents average for your bedroom band in that authority. PIPR publishes an average (a mean), not quartiles, so we draw a ±15% band around it and say so on the result.
- Region, then England. If PIPR suppresses that bedroom band for the authority, we use the same average for the region, and failing that for England. The result labels the level used, and the confidence is always “low” for a synthesised band.
The output is a three-figure range — lower quartile, median, upper quartile (or the average with its ±15% band) — for properties of your type in your area. Your proposed rent is then placed on that range and classified into one of four bands: below market, around market, possibly above market or strongly above market. Postcodes in Scotland, Wales and Northern Ireland get no verdict: the law is different there.
Update cadence
The ONS publishes the Price Index of Private Rents monthly, and the London district statistics less often. We update RentCharter when a new edition is published. Every result page shows the publication date of the underlying data so you can confirm how current it is.
What this is not
- Not a regression on live listings. We don't predict rent from listing features (square footage, EPC, distance to a tube station). We compare against a published distribution.
- Not a regulated valuation. The output is indicative. A formal valuation would require a RICS-registered surveyor visiting the property.
- Not a substitute for the tribunal. A First-tier Tribunal decision uses comparable evidence specific to the individual property and area. Our check is a fast first-pass that tells you whether the proposed figure is in the right ballpark.
- Not personalised legal advice. Every page is labelled “information only, not legal advice” — and we signpost to Shelter and Citizens Advice for advice on your specific situation.
Showing uncertainty
Every comparison comes with a confidence label that reflects:
- The size of the underlying sample for your district and bedroom count, where the ONS publishes one.
- Whether the lookup was postcode-district, local-authority, regional or England-wide — every synthesised band is labelled low confidence, however official the average behind it.
A “low confidence” label doesn't mean the result is wrong — it means the underlying public sample is thin (typically rural local authorities or rare property types). In those cases, tribunal-grade evidence usually comes from agent-supplied comparables rather than published statistics, and we say so.
What we plan to add
The roadmap is open. The current priority list:
- Tenant-submitted rents, moderated and aggregated, to fill in the gaps the published statistics don't cover.
- Case outcome data so results can show how comparable increases were resolved.
- Licensed listing snapshots for cross-validation against published statistics.
- Letting agent-submitted comparable evidence, attributable and dated.
Audit and reproducibility
Every check produces an evidence pack. The pack shows the underlying comparison range, the publication date of the data, the lookup method we used, and the confidence label. If you challenge a rent to the First-tier Tribunal, that pack is what you attach — and any surveyor or tribunal member can re-derive the comparison from the same public source data.
Questions, corrections, suggestions
If you spot something wrong or you'd like to suggest a methodological improvement, write to elliot@rentcharter.org.