Section 5(1)(c) in The Customs Valuation (Determination of Price of Imported Goods) Rules, 1988.
(c)where no sale referred to in Clause (b) of sub-rule (1) of this rule, is found, the transaction value of identical goods sold at a different commercial level or in different quantities or both, adjusted to take account of the difference attributable to commercial level or to the quantity or both, shall be used, provided that such adjustments shall be made on the basis of demonstrated evidence which clearly establishes the reasonableness and accuracy of the adjustments, whether such adjustment leads to an increase or decrease in the value.