No marking requirement exists for display of either the MX number of the Mexico-domiciled carrier or the MC number of the U.S. carrier. The vehicle must be marked in accordance with 49 CFR 390.21(a) that requires the legal name or a single trade name of the motor carrier operating the self-propelled CMV, and the identification number issued by FMCSA to the motor carrier preceded by the letters “USDOT.” For the Mexico-domiciled motor carrier, the USDOT identification number must be followed by either the distinctive “Z” denoting commercial zone operations or the “X” denoting operations beyond the commercial zone, depending on the type of authority the company has received.
If the name of any person other than the operating carrier appears on the CMV, the name of the operating carrier must be followed by the legal name or a single trade name of the motor carrier operating the self-propelled CMV, the identification number issued by FMCSA to the motor carrier preceded by the letters “USDOT" and be preceded by the words “operated by."