CENVAT credit documentation requirements determine admissibility: specified invoices, challans, and records trigger credit eligibility and return obligations. CENVAT credit is allowed only on specified documents-such as manufacturer, importer, dealer invoices, bills of entry, customs certificates, service provider invoices, supplementary invoices and input service distributor documents-and is excluded where additional duty or tax is recoverable due to fraud or contravention. Documents must contain prescribed particulars or, if incomplete, may be accepted by the Deputy/Assistant Commissioner when goods or services are received and accounted for. Claimants bear the burden of proof and must maintain detailed records of receipts, consumption, values, duty/tax paid and credits, while complying with specified periodic return filing and revision provisions.