Proof of customs duty payment: attested TR 6 challan copies suffice for advance authorization regularisation, originals not routinely required. For regularising shortfall under the Advance Authorisation Scheme, Regional Authorities may accept an attested copy of the TR 6 challan as evidence of customs duty and interest payment for issuance of the EODC; the original need not be insisted upon unless reasons are recorded. After EODC issuance, a copy of the challan with the EODC must be forwarded to the Customs Authority at the Port of Registration with a specific endorsement for cross verification before redemption of the Bank Guarantee or Legal Undertaking.