Rectification of advance ruling: authorities may amend orders for apparent errors, subject to hearing before increasing tax liability. Authority or Appellate Authority may amend orders to rectify errors apparent on the face of the record, on its own motion or when notified by concerned officers or the applicant/appellant, within a prescribed time limit; provided that any rectification that would enhance tax liability or reduce admissible input tax credit requires giving the applicant or appellant an opportunity of being heard.