Rectification of advance ruling permits correcting apparent errors, with a hearing required before increasing tax or cutting input credit. Rectification permits the Authority or Appellate Authority to amend orders to correct errors apparent on the face of the record, whether noticed by the authority or brought by officers or the applicant/appellant within a prescribed time limit, and requires that any amendment increasing tax liability or reducing admissible input tax credit not be made without granting the applicant or appellant an opportunity to be heard.