 In practice, it has always been set at two years prior to the start of the list, so that for the 2005 rating list it is 1 April 2003.Hereditament is a legal term for a unit of property, which often appears to be synonymous with simply "property", in the bricks and mortar sense of the word.The concept of hereditament in rating law has developed along with that of rateable occupation through case law, as no single statute has defined it adequately.