# Valuation and Rating (Scotland) Act 1956, Paragraph 4


(1) For the basic year and each year subsequent to the basic year each Gas Board’s basic rateable valuation shall be adjusted in accordance with the following provisions of this paragraph, and such basic rateable valuation as so adjusted shall be the rateable valuation of that Board’s undertaking for that year.
(2) For each such year each Gas Board shall—
(a) estimate and certify the total number of therms supplied by the Board to consumers in Scotland during the twelve months ending with the thirty–first day of March falling within the immediately preceding year, and
(b) calculate and certify the amount by which that total exceeds, or falls short of, the Board’s standard number of therms;
and the Board’s basic rateable valuation shall be adjusted for that year by multiplying it by the fraction of which—
(i) 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
(ii) the denominator is the Board’s standard number of therms.

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Source: https://www.legislation.gov.uk/ukpga/Eliz2/4-5/60/schedule/FOURTH/paragraph/4 (the official version)
Page: https://openlegislation.uk/valuation-and-rating-scotland-act-1956/schedule-FOURTH/paragraph-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.