The Assessor is responsible for the preparation and maintenance of the Council Tax Valuation List, which places each domestic property ("dwelling") in one of eight valuation bands. The band reflects the Assessor's opinion of the property's open market as at 1st April 1991, subject to a number of important statutory assumptions. Properties built since 1991 must still be banded with regard to the value they would have had if they had existed in 1991.