49 CFR § 385.301 - What is a motor carrier required to do before beginning interstate operations?
(a) Before a motor carrier of property or passengers begins interstate operations, it must register with FMCSA and receive a USDOT Number. In addition, for-hire motor carriers must obtain operating authority from FMCSA, unless exclusively providing transportation exempt from the commercial registration requirements in 49 U.S.C. chapter 139. Both the USDOT Number and operating authority are obtained by following registration procedures described in 49 CFR part 390, subpart E. Part 365 of this chapter provides detailed instructions for obtaining operating authority.
(c) The regulations in this subpart do not apply to a Mexico-domiciled motor carrier. A Mexico-domiciled motor carrier of property or passengers must register with FMCSA by following the registration procedures described in 49 CFR parts 365, 368 and 390. Parts 365 (for long-haul carriers) and 368 (for commercial zone carriers) of this chapter provide detailed information about how a Mexico-domiciled motor carrier may obtain operating authority.