The Valuation Office Agency is responsible for setting the bands for Council Tax properties and the Rateable Values for Non-Domestic Properties.
If you wish to appeal against your banding or rateable value you should contact the Valuation Office and not the Council. You must continue to pay your existing bill while you are waiting for the results of an appeal.
The address of the office that values properties in the Wigan area is shown below. More information about the Valuation Office Agency (external link) and an on-line valuation list of rateable values and Council Tax bands for the whole country is available on their web site.