Which number identifies a motor carrier with FMCSA registration?

• A. DOT# (Department of Transportation number)
• B. MC# (Motor Carrier Number)
• C. Authority
• D. COI (Certificate of Insurance)

Answer: (B)

FMCSA uses two identifiers for motor carriers: a USDOT number and a Motor Carrier (MC) number. The MC number is the one that specifically flags the carrier’s authority to operate as a motor carrier when you’re looking at FMCSA registration. It’s the numeric tag tied to their operating authority in FMCSA systems like SAFER. The USDOT number (often shown as a DOT#) is a broader identifier used for safety compliance, not the operating authority itself. A COI is an insurance certificate, not an identifier. Authority refers to the permission granted, not a number. So the best identifier for a motor carrier’s FMCSA registration is the Motor Carrier number.