law: Custom Act, 1962 
  25.
  
  Power to Grant Exemption from Duty. – 
  (1)
  
  If the Central Government is satisfied that it is necessary in the public
  
  interest so to do, it may, by notification in the Official Gazette, exempt
  
  generally either absolutely or subject to such conditions (to be fulfilled
  
  before or after clearance) as may be specified in the notification goods of any
  
  specified description from the whole or any part of duty of customs  leviable thereon.
  (2)
  
  If the Central Government is satisfied that it is necessary in the public
  
  interest so to do, it may, by special order in each case, exempt from payment
  
  of duty, for reasons to be stated in such order, any goods, of strategic or
  
  secret nature, or for charitable purpose, on which duty is leviable .
  (3)
  
  An exemption under sub-section (1) or sub-section (2) in respect of any goods from
  
  any part of the duty of customs leviable thereon (the
  
  duty of customs leviable thereon being hereinafter
  
  referred to as the statutory duty) may be granted by providing for the levy of
  
  a duty on such goods at a rate expressed in a form or method different from the
  
  form or method in which the statutory duty is leviable 
  
  and any exemption granted in relation to any goods in the manner provided in
  
  this sub-section shall have effect subject to the condition that the duty of
  
  customs chargeable on such goods shall in no case exceed the statutory duty.
  Explanation
  
  :  "Form or method", in relation
  
  to a rate of duty of customs, means the basis, namely, valuation, weight,
  
  number, length, area, volume or other measure with reference to which the duty
  
  is leviable .
  (4)
  
  Every notification issued under sub-section (1) shall
  (a) unless otherwise provided, come into force on the date of its issue
  
  by the Central Government for publication in the Official Gazette;
  (b) also be published and offered for sale on the date of its issue by
  
  the Directorate of Publicity and Public Relations of the Board, New Delhi.
  (5)
  
  Notwithstanding anything contained in sub-section (4), where a notification
  
  comes into force on a date later than the date of its issue, the same shall be
  
  published and offered for sale by the said Directorate of Publicity and Public
  
  Relations on a date on or before the date on which the said notification comes
  
  into force.