Certification of Origin: rules on form, validity, retrospective issue, certified copies and minor discrepancies under trade agreement Proofs of Origin must be in English and follow the prescribed Certificate of Origin form with a unique serial number; they are valid for a single import and must reference commercial invoice details and be submitted within their validity. Customs may accept expired Proofs for preferential treatment where delay is due to force majeure and the goods were imported before expiry. Certificates are normally issued at exportation but may be issued retrospectively within twelve months with the endorsement 'ISSUED RETROSPECTIVELY' and written reasons; certified true copies may replace lost originals within one year. Minor typographical or formatting discrepancies that do not affect authenticity do not invalidate Proofs, while signature or seal discrepancies are excluded from this tolerance.