General Rate Act 1967

4 (1) For each year each Gas Board shall—

(a) estimate the number representing the total number of therms supplied by the Board or the Gas Council in the penultimate year to consumers in the Board's area less one-half the number of therms in any gas purchased by the Board in the penultimate year otherwise than from the Gas Council; and

(b) calculate and certify the amount by which that estimated number exceeds, or falls short of, the Board's standard number of therms ;

and the Board's basic total of rateable values shall be adjusted for that year by multiplying it by the fraction of which the numerator is the Board's standard number of therms increased by one-fifth of the said excess or, as the case may be, decreased by one-fifth of the said deficiency, and the denominator is the Board's standard number of therms.

(2) For the purposes of the foregoing sub-paragraph, gas purchased by the Gas Council from any person other than a Gas Board shall be treated as having been purchased by the Gas Boards in the respective quantities settled by a scheme or schemes made from time to time by the Gas Council and approved by the Minister of Power.