An MC number is the docket number FMCSA assigns when it grants a company interstate operating authority. Operating authority is separate from a USDOT number. It defines what kind of operation a company may run, such as for-hire carrier or broker, and sets the insurance or financial security the company must maintain. Depending on the authority type, the docket number carries an MC, FF or MX prefix, and companies that need authority must hold it in addition to a USDOT number.
The future of MC numbers has been in flux. FMCSA treats the USDOT number as the unique identifier for regulated companies, and earlier plans for its registration overhaul included retiring MC and FF numbers. In an April 2026 policy notice on the new Motus registration system, FMCSA said the broader rollout would not eliminate those numbers, following stakeholder concerns, and that it would consider the change in later releases. FMCSA's own guidance says Motus continues to issue docket numbers with the same prefixes, existing numbers will not change, and any elimination would be proposed through future rulemaking. No retirement date has been set.
For dealers and auctions vetting a broker or carrier, it is reasonable to ask for both numbers and confirm them in FMCSA's public records. Related terms: FMCSA and broker surety bond.