About Bandplain
Bandplain is a research tool for households in England and Wales. It asks whether a council tax band looks high compared with similar homes, then, if you want it, writes that comparison down so you can challenge the band yourself.
How a check works
You give a postcode, a house number or name, the property type, the number of bedrooms, and whether there has been an extension or conversion. We look up one band for that address and cache it. We then look for sales in the same postcode district, keep the ones that are a similar type and size, and index the prices back to 1 April 1991 in England or 1 April 2003 in Wales.
The verdict is deliberately cautious. A large extension stops us calling a band too high. A value within 8% of the band edge stays borderline. If the indexed sales sit above the current band, we say the band may be low, because a review can move it up.
Data we use
- UK House Price Index, HM Land Registry and the Office for National Statistics, under the Open Government Licence. The back-series reaches 1991. Local authority series generally start in 1995, so England estimates use the regional index.
- Price Paid Data, when you load the official file, is also Open Government Licence. The copy you can try here ships with fictional sample sales, clearly labelled, so the flow works before that file is imported.
- Billing authorities come from the ONS Local Authority Districts (April 2025) names and codes, Open Government Licence.
Data we do not use
Council tax bands are not scraped and not bulk-downloaded. The Valuation Office Agency says bulk disclosure is unlawful. Lookups go through a provider interface: a mock list for this demo, and a stub for a paid per-address API such as Homedata.
Energy Performance Certificate addresses are not used. Non-address EPC fields are published for energy research, but the address and postcode are restricted to energy-performance purposes. Matching a home for a council tax pack is outside that licence, so floor area is not pulled in.
Notes prepared November 2026. This page is not a valuation and not legal advice.