DOT and MC numbers are the FMCSA identifiers of U.S. trucking: the DOT number registers the carrier for safety oversight, and operating authority (historically the MC number) licenses for-hire interstate work. Mexico-only carriers have neither, which reshapes vetting.
The DOT number and MC number are the identity keys of U.S. trucking. The USDOT number registers a carrier with FMCSA for safety oversight; operating authority, historically expressed as the MC number, licenses a carrier to haul for-hire interstate freight (FMCSA has been consolidating identifiers around the USDOT number, but the industry still speaks in MC numbers). Together they anchor everything U.S. vetting checks: authority status, insurance filings, safety scores, and authority age.
Cross-border, the crucial fact is who has them. Mexican carriers operating only within Mexico have neither. Mexico-domiciled carriers running into U.S. border commercial zones register with FMCSA under specific certificates (the OP-2 path), and a smaller set holds long-haul authority beyond the zones. Mexican carrier identity at home anchors instead to the RFC and SICT permits.
Vet the entity that touches each leg with that leg's identifiers: the U.S.-side carrier or transfer by DOT/MC and safety record, the Mexican linehaul carrier by its Mexican artifacts. Dual-entity carriers, a U.S.-authority entity paired with a Mexican fletera under common ownership, are normal and legitimate in this market, but each entity must hold its own credentials for its own role, and the entity named on your rate con should match the one whose authority and insurance actually cover the move.
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