A NAFTA Certificate of Origin is not required for shipments to Mexico or Canada. The exporter should only prepare a NAFTA Certificate if the product qualifies for preferential tariff treatment under the NAFTA rules of origin. A NAFTA Certificate of Origin is not required for the commercial importation of a good valued at less than US$1,000. However, for goods to qualify for NAFTA preferential duties, the invoice accompanying the commercial importation must include a statement certifying that they qualify as originating goods under the NAFTA rules of origin. The statement should be handwritten, stamped, typed on or attached to the commercial invoice. This exception is valid as long as the shipment does not form part of a series of importations that may reasonably be considered to have been undertaken or arranged for the purpose of avoiding the Certification requirement.