If you operate commercial motor vehicles (CMVs) that transport passengers or cargo across state lines, you need to register with the Federal Motor Carrier Safety Administration (FMCSA) and obtain a USDOT number. This unique identifier helps the FMCSA monitor and collect safety information on companies through audits, compliance reviews, crash investigations, and inspections. But what exactly is the USDOT number, and when do you need to get one? You must obtain a USDOT number if you have a CMV that: Transports hazardous materials requiring a safety permit within a state Has a gross vehicle weight rating over 10,001 pounds Transports more than 8 passengers (including the driver) for compensation Transports more than 15 passengers (including the driver) without compensation Additionally, that vehicle must be used for interstate commerce, meaning trade, traffic, or transportation: Between a place in one state and somewhere outside that state (even if outside the US) Through another state or place outside the US between two places inside a state Originating or terminating outside a state or the US between two places inside a state  So in summary, if your commercial vehicle meets the weight, passenger, or hazardous materials criteria AND crosses state lines for business purposes, you need to register it with the FMCSA and obtain a USDOT number. This allows the agency to keep tabs on your safety record. Noncompliance can result in fines or put your ability to operate at risk. so ensuring you have a USDOT number when required is crucial.