Notwithstanding anything contained in this Act, the Administrator may, by notification in the Official Gazette and subject to such conditions, if any, as may be specified therein, specify the point of sale at which any goods or class of goods may be taxed, and on the issue of such notification, the points of sale in relation to any such goods or class of goods other than the point of sale so notified, shall be exempt from payment of tax under this Act:
     Provided that no such exemption shall be allowed unless a true declaration duly filled and signed by the registered dealer by whom the goods are sold and containing the prescribed particulars in the prescribed form obtainable from the prescribed authority is furnished in the prescribed manner and within the prescribed time, by the dealer who purchases the goods:
     Provided further that the Administrator may, if he is of opinion that it is necessary in the public interest so to do, by notification in the Official Gazette, exempt, subject to such restrictions and conditions as may be specified therein, any dealer or class of dealers from furnishing a declaration under the first proviso.