Retrospective excise levy: CENVAT credit allowed only with prescribed duty documents and certified stock records. Retrospective excise liability arising from packing, repacking and related operations permits manufacturers to utilise eligible input duties as CENVAT credit for payment of duty on final products, but only upon production of prescribed duty paying documents. Opening stocks as at the cut off must be declared on internal records authenticated by a chartered accountant and company directors; input credit on such stocks is allowed on the basis of available invoices/import documents. Supplementary invoices/challans for stock transfers and monthly statements of production, clearances and credit balances are required to support verification. Retail spares are valued under MRP while original equipment follows transaction value; interest waiver is not available under existing law.