CENVAT credit utilisation requirement: manufacturers must exhaust CENVAT first; optional account current credit subject to verification and reversal. Amendments condition full-exemption availability on first utilising all CENVAT credit at month-end toward duty and paying the cash balance. Where some goods are non-exempt, refunds are limited to duty paid less attributable CENVAT credit. Manufacturers may opt to credit duty paid (other than by CENVAT) into an account current for later deemed-cash payment, subject to written annual election, monthly crediting and statement submission, officer verification and determination of refundable amounts, reversal of excess credits, forfeiture on non-compliance, and recovery treatment for irregular or excess credits.