law: Custom Act, 1962 
  149.
  
  Amendment of Documents. – 
  Save
  
  as otherwise provided in sections 30 and 41, the proper officer may, in his
  
  discretion, authorise any document, after it has been presented in the custom
  
  house to be amended :
  Provided
  
    that no amendment of a bill of entry or
  
  a shipping bill or bill of export shall be so authorised to be amended after
  
  the imported goods have been cleared for home consumption or deposited in a
  
  warehouse, or the export goods have been exported, except on the basis of
  
  documentary evidence which was in existence at the time the goods were cleared,
  
  deposited or exported, as the case may be.