6(1)For the purposes of this Schedule the aggregate net annual value of a rating area for any year shall be taken to be the aggregate, as estimated and certified by the Commissioners of Inland Revenue (hereinafter referred to as " the Commissioners") of the rateable value (or, where that value differs from the net annual value, of the net annual value) of every hereditament the rateable value of which appears in the valuation list for the area on the first day of April in the preceding year, other than any hereditament so appearing in pursuance of section twelve of this Act or section six of the Act of 1955, and of the values appearing to the Commissioners to represent the net annual values of hereditaments occupied by or on behalf of the Crown.
(2)For the purposes of this Schedule the aggregate net annual value for any year of the area of an Electricity Board, or of any part of a rating area of which part only is comprised within the area of an Electricity Board, shall be ascertained by such aggregation or apportionment as may be required; and any apportionment under this sub-paragraph shall be made, and the result thereof certified, by the Commissioners.
(3)References in this Schedule to the area of an Electricity Board shall be construed, in relation to the Generating Board, as references to the whole of England and Wales.