A person who purports to act as or on behalf of a corporation but who knows that there was no incorporation under this chapter is jointly and severally liable for all liabilities created while so acting.
Mont. Code Ann. § 35-2-215, under Formation -- Articles of Incorporation Bylaws -- Amendments.
Mont. Code Ann. § 35-2-215
A person who purports to act as or on behalf of a corporation but who knows that there was no incorporation under this chapter is jointly and severally liable for all liabilities created while so acting.