In the past year, the Mexican Government (SAT) has issued questionnaires to exporters from the United States which provided a NAFTA Certificate of Origin to the Mexican importer. The North American Free Trade Agreement (NAFTA) Certificate of Origin is always created and signed by the U.S. exporter or producer, and always provided to the Mexican importer at the time of importation so that the Mexican importer may importer the merchandise into Mexico without paying any customs duties. Years later, the Mexican Government may send a questionnaire to first the U.S. exporter, and then the Mexican importer, demanding proof that the merchandise really "originated" in the United States and properly entered Mexico without any payment of customs duties.
The problems are (1) the U.S. exporter falsely completed the NAFTA Certificate of origin either intentionally or by ignorance, (2) the U.S. exporter relied on the U.S. producer who provided misleading information to the U.S. exporter, or (3) the records establishing that the merchandise originated in the United States are not available.
I usually recommend the U.S. exporter who received a letter from the SAT of the Mexican Government to respond. Moreover, it is best to seek the assistance of the supplier of the merchandise to the U.S. exporter and the Mexican importer. If the questionnaire is not answered properly and timely, the SAT will deny the NAFTA preferential treatment, and demand payment of customs duties, late fees, interest, and penalties from the Mexican importer, plus perhaps antidumping duties. The Mexican importer may end up paying those charges to the Mexican Government agency and then seek full reimbursement, plus legal fees, from the U.S. exporter.