Do I need an MC number or just a USDOT number?
Most for-hire interstate motor carriers need both. The USDOT is the safety-tracking ID; the MC is the for-hire interstate operating-authority ID. Private carriers (hauling their own freight) need only the USDOT. Pure intrastate carriers may need neither under federal rules but face state-level requirements.
The USDOT number is permanent and assigned to any operator of a commercial motor vehicle in interstate or certain intrastate commerce. It tracks DOT inspections, crashes, and safety audit history across the carrier's lifetime.
The MC number is the operating-authority identifier issued under 49 USC §13902. It is required to haul property or passengers FOR HIRE in interstate commerce — meaning across state lines for compensation. Private carriers hauling their own goods do not need an MC.
In practice, three categories: (1) for-hire interstate carrier — USDOT + MC; (2) private interstate carrier — USDOT only; (3) intrastate-only carrier — depends on state, but typically state intrastate authority + USDOT (if state requires).
Brokers and freight forwarders need MC-B / MC-FF authority + USDOT. The FMCSA registration page is where both numbers issue from in a single workflow.