VATRES6500 - Personal exports - retail exports: Assurance at the retailer: Evidence of export
You need to ensure any claim for zero-rating goods sold under VAT retail export scheme is substantiated by a correctly certified form VAT 407, or an approved version or adapted retail export scheme invoice (VAT refund document). To comply with EC legislation, the VAT refund document must be certified at the final point of exit from the EC. (Overseas certification at the point of destination outside the EC was withdrawn in January 1992).
Certification of the VAT refund documentation will be at the final point of exit from the EC, subject to the application of any of the exceptions outlined in VATRES4000
Alternative evidence of export
No form of overseas stamping is acceptable unless exceptional circumstances exist. You should report any case you cannot deal with to the Retail UoE.