Revision power over subordinate tax orders permits non prejudicial corrections subject to limitation, fee, and appeal bars. Section 264 authorises the Principal Commissioner or Commissioner to call for records and revise subordinate orders (excluding those under section 263), either suo motu or on assessee application, conduct inquiries, and pass orders not prejudicial to the assessee. Revision is constrained by limitation periods, required fees, exclusions for pending appeals and appeal periods, and specified exclusions and computation rules for time when stays or re hearing opportunities arise.