Section 15 of Customs Act prescribes that rate of duty and tariff valuation applicable to imported goods shall be
the rate and valuation in force at one of the following dates (a) if the goods are entered for home consumption,
the date on which bill of entry is presented (b) in case of warehoused goods, when Bill of Entry for home
consumption is presented u/s 68 for clearance from warehouse and (c) in other cases, date of payment of duty.