31 CFR §8.29

1. (a)General. Individuals may appear on their own behalf and may otherwise appear without enrollment, providing they present satisfactory identification, in the following classes of cases:
   1. (1)An individual may represent another individual who is his or her regular full-time employer, may represent a partnership of which he or she is a member or a regular full-time employee, of may represent without compensation a member of his or her immediate family.
   2. (2)Corporations (including parent corporations, subsidiaries or affiliated corporations), trusts, estates, associations, or organized groups may be represented by bona fide officers or regular full-time employees.
   3. (3)Trusts, receiverships, guardianships, or estates may be represented by their trustees, receivers, guardians, administrators, executors, or their regular full-time employees.
   4. (4)Any government unit, agency, or authority may be represented by an officer or regular employee in the course of his or her official duties.
   5. (5)Unenrolled persons may participate in rulemaking as provided in 5 U.S.C. 553.
2. (b)Special appearances. The Director, subject to conditions he or she deems appropriate, may authorize any person to represent a party without enrollment, for the purpose of a particular matter.