If you think your rateable value is wrong, you can apply to the Valuation Officer to change it. To do this, you will need to make a 'proposal' to alter the rating list.
Forms for this purpose are available from your local Valuation Office:
Valuation Office Agency
Castle Meadow Road
Tel : 03000 501 501
If the Valuation Officer agrees with your proposal, or if you can reach agreement on another figure, the value will be changed. If he does not agree, or the matter is still unresolved after 3 months, the dispute will be passed to the local Valuation Tribunal as a formal appeal.
However, in many cases it may still be possible for an agreement to be reached before the tribunal hearing itself, as discussions can continue.
See the link and check your summary valuation which will show how your present assessment has been valued
You have to pay rates on the rateable value shown in the rating list even if you have appealed against it. But provided you have kept up with your payments, any overpayment you are found to have made when an appeal is settled will be refunded with any interest applicable.