Section 9(1)(b) in The Customs Valuation (Determination of Price of Imported Goods) Rules, 1988.
(b)the value, apportioned as appropriate, of the following goods and services where supplied directly or indirectly by the buyer free of charge or at reduced cost for use in connection with the production and sale for export of imported goods, to the extent that such value has not been included in the price actually paid or payable, namely :(i)materials, components, parts and similar items incorporated in the imported goods;(ii)tools, dies, moulds and similar items used in the production of the imported goods;(iii)materials consumed in the production of the imported goods;(iv)engineering, development, art work, design work, and plans and sketches undertaken elsewhere than in India and necessary for the production of the imported goods;