Rectification of advance ruling: correction allowed for apparent errors but hearing required before increasing tax liability. The Authority or Appellate Authority may amend its orders to rectify an error apparent on the face of the record, whether noticed on its own motion or brought to its notice by officers or the applicant/appellant, provided this is done within six months of the order; proposed rectifications that would enhance tax liability or reduce admissible input tax credit require giving the applicant/appellant an opportunity to be heard.