Bar of limitation for imposing penalties: penalty orders are time barred unless issued within six months after specified post quarter events. Bar of limitation requires penalty orders to be passed within six months from the end of the quarter in which specified events occur (completion of proceedings, receipt of revision or appeal orders by the jurisdictional Principal Commissioner or Commissioner, or issuance of notice). Penalty orders may be revised to give effect to a revised assessment on appeal or revision, but only after affording the assessee a hearing and within the same six month post quarter limitation; certain periods (rehearing under the proviso to section 129 and court stay periods until certified vacation is received) are excluded from the limitation computation.