Verification of Certificates of Origin requires concrete reasons for doubt and specific information requests before seeking external verification. Verification under CAROTAR must be based on a proper officer's reasoned belief that originating criteria are unmet or a preferential claim is invalid; requests under Rule 6(1)(b) must state specific grounds and precise information required from the Verification Authority. Representative CoOs should be selected where multiple identical items are under review, and prior verifications of the same manufacturer's product may be applied to subsequent consignments unless there is reason to believe origin has changed. RMS interdiction alone does not justify verification; prescribed procedures, formats and timelines must be followed.