If there is a change in the rate of tax--

(a) a taxable supply made (***) by a registered person shall be charged to tax at such rate as
is in force at the time of supply;

(b) imported goods shall be charged to tax at such rate as is in force,--

(i) in case the goods are entered for home consumption, on the date on which a bill of
entry is presented under section 79 of the Customs Act, 1969 (IV of 1969);

(ii) in case the goods are cleared from warehouse, on the date on which a bill of entry for
clearance of such goods is presented under section 104 of the Customs Act, 1969 (IV
of 1969):

Provided that where a bill of entry is presented in advance of the arrival of the
conveyance by which the goods are imported, the tax shall be charged as is in
force on the date on which the manifest of the conveyance is delivered:

Provided further that if the tax is not paid within seven days of the presenting of the
bill of entry under section 104 of the Customs Act, the tax shall be charged at the rate as is in force on the date on which tax is actually paid.