Credit of duty on returned goods permitted when goods are received before the duty payment deadline, enabling input credit access. Credit of duty on goods returned or rejected and received back into the factory before the prescribed duty payment date is allowable under the Central Excise Rules because duty is treated as deemed paid and the invoice for returned goods is a valid document to avail credit; the assessee may also avail credit on its own invoice, and the mechanism is revenue neutral as duty must be discharged by the statutory due date.