Revision of orders: competent authority may revise subordinate tax orders subject to limitation, appeal bar, and procedural safeguards. The Competent Authority (Principal Chief Commissioner, Chief Commissioner, Principal Commissioner or Commissioner) may call for records, make inquiries and pass non prejudicial revisionary orders suo motu or on application for orders outside section 377. Time limits restrict suo motu revision to within one year of the original order, and assessee applications must be made within one year from communication or knowledge, subject to sufficient cause extensions. Revision is barred where an appeal lies and has not been pursued or where an appeal is pending. Applications require a fee and must be disposed within prescribed timeframes with limited exclusions and minimum periods; revision may also follow appellate directions.