Pre-authentication of invoices is not required; dealers must maintain records for Cenvat credit eligibility. Maintenance of records by first stage and second stage dealers is required for entitlement to input credit under the Cenvat Credit Rules; dealers must keep records showing supplies from duty-paid stock and pro rata duty indicated on invoices. There is no statutory provision for pre-authentication of invoices issued by second stage dealers or dealers of imported goods by Central Excise officers, and such pre-authentication should not be insisted upon.