As per Section 149 of the Customs Act, 1962, ‘no amendment of a bill of entry or a shipping bill or bill of export shall be 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.’ So, the law allows amendment to a shipping bill or bill of entry even after the clearance of goods but only on the basis of documents that existed at the time of the clearance of goods. As per Section 154 of the Customs Act, 1962, ‘clerical or arithmetical mistakes in any decision or order passed by the Central Government, the Board or any officer of customs under this Act, or errors arising therein from any accidental slip or omission may, at any time, be corrected by the Central Government, the Board or such officer of customs or the successor in office of such officer, as the case may be.’ Thus, the law allows correction of any mistakes that are apparent on the face of the document that do not require any investigation. No time limits are stipulated in either of the said Sections.
Hence you may like to approach the concerned Customs Port/Airport authorities wherefrom the goods were exported.