Mont. Code Ann. § 35-8-1301

Professional limited liability companies may be organized under this part only for the purpose of rendering professional services and services ancillary to professional services within a single profession, except that a professional limited liability company may be organized for the purpose of rendering professional services within two or more professions and for any purpose or purposes for which companies may be organized under this chapter to the extent that the combination of professional purposes or professional and business purposes is permitted by the licensing laws and rules of this state applicable to the professions.