Guide
Your band is frozen at what the property was worth in 1991, not today. It's a big monthly cost, and the same band costs different amounts depending on the council.
Council tax is the annual charge you pay your local council, spread over monthly instalments. Every home sits in a band from A to H, and the band, plus where you live, sets the bill.
This catches everyone out: an English property's band reflects what it would have sold for on 1 April 1991, not what it's worth now. So a modern flat worth £600,000 today can sit in a middling band, because its 1991 equivalent was modest. The band never gets re-based, it just carries the 1991 valuation forward. (buyerside estimates the band by deflating our valuation back to 1991 prices.)
These are the value ranges, at 1 April 1991 prices, set by the Valuation Office Agency:
The band only sets the ratio. Each council picks its own Band D rate every year, and the other bands are fixed multiples of it, so an identical Band D home costs noticeably more in one borough than another. Check the specific council's rate for the real number, and budget for it rising each April.
You can look up any home's band, and if you think it's wrong, challenge it with the Valuation Office Agency. You'll need evidence, usually the bands of near-identical neighbouring homes. A successful challenge can also cut the band for the whole terrace, so it's worth a look if yours sits above its neighbours.