The government Valuation Office Agency (VOA) sets the rateable value of business premises by using property details such as rental information. The rateable value and the business rates multiplier (set by central government) is used to calculate your annual business rates bill.
The VOA regularly reassesses and updates the rateable values of all business properties, usually every five years. This is called a Revaluation.
Revaluation is done in order to maintain fairness in the system by redistributing the total amount payable in business rates, reflecting changes in the property market.
Revaluation does not raise extra revenue overall.
The Rating List and further information about rateable values is available from the GOV.UK - Valuation Office Agency.