Limitation period for penalty orders: revised timelines and procedural safeguards clarified under Section 275, including revision and computation rules. The statute sets fixed limitation periods for passing, revising or dropping penalty orders, triggered by completion of proceedings, receipt of appellate or revision orders, or issuance of penalty notice, with the later applicable cutoff controlling. Revision of penalty orders is permitted to give effect to assessments revised on appeal or revision, subject to the assessees' right to be heard and to exclusion of interruption periods (rehearing time, immunity periods, and court stays) when computing limitation.