19 CFR §148.114
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
One copy of the validated Customs Form 255 shall be returned to the vendor. The vendor shall place the form in an envelope, affix it to the outside of the shipment, and clearly mark the outside of the shipment “Unaccompanied Tourist Shipment.”