Md. Code, Tax - General § 11–703

An applicant for a license to engage in the business of an out–of–state vendor, to engage in the business of a retail vendor, or to engage in the business of a marketplace facilitator shall submit an application to the Comptroller:

(1) for each place of business in the State where the applicant sells tangible personal property, a digital code, a digital product, or a taxable service;

(2) if the applicant has no fixed place of business and sells from 1 or more vehicles, for each vehicle; or

(3) if the applicant has no fixed place of business and does not sell from a vehicle, for the place designated as the address to which notices are to be mailed.