Section 9(1)(b) in The Special Economic Zones Rules, 2003
(b)the depreciation in value shall be allowed for the period from the date of commencement of commercial production of the special economic zone unit, or where such capital goods have been received in the special economic zone unit after such commencement of commercial production, from the date such goods have come into use for commercial production, to the date of presentation of bill of entry for home consumption;