Cal. Civ. Proc. Code § 116.540

(a) Except as permitted by this section, no individual other than the plaintiff and the defendant may take part in the conduct or defense of a small claims action.
(b) Except as additionally provided in subdivision (i), a corporation may appear and participate in a small claims action only through a regular employee, or a duly appointed or elected officer or director, who is employed, appointed, or elected for purposes other than solely representing the corporation in small claims court.
(c) A party who is not a corporation or a natural person may appear and participate in a small claims action only through a regular employee, or a duly appointed or elected officer or director, or in the case of a partnership, a partner, engaged for purposes other than solely representing the party in small claims court.
(d) If a party is an individual doing business as a sole proprietorship, the party may appear and participate in a small claims action by a representative and without personally appearing if both of the following conditions are met:
1. (1) The claim can be proved or disputed by evidence of an account that constitutes a business record as defined in Section 1271 of the Evidence Code, and there is no other issue of fact in the case.
2. (2) The representative is a regular employee of the party for purposes other than solely representing the party in small claims actions and is qualified to testify to the identity and mode of preparation of the business record.
(e) A plaintiff who is a service member is not required to personally appear, and may submit declarations to serve as evidence supporting their claim, appear via video appearance, or allow another individual to appear and participate on their behalf, if the service member is assigned to a location more than 100 miles from the court where the action is proceeding, or is otherwise unable to personally appear due to the performance of military duty, the representative is serving without compensation, other than compensation from the United States or the State of California, and, except as to representatives who are employed by the United States or the State of California, the representative has appeared in small claims actions on behalf of others no more than four times during the calendar year. The defendant may file a claim in the same action in an amount not to exceed the jurisdictional limits stated in Sections 116.220, 116.221, and 116.231.
(f) A party incarcerated in a county jail, a Department of Corrections and Rehabilitation facility, or a Division of Juvenile Facilities facility is not required to personally appear, and may submit declarations to serve as evidence supporting their claim, or may authorize another individual to appear and participate on their behalf if that individual is serving without compensation and has appeared in small claims actions on behalf of others no more than four times during the calendar year.
(g) A defendant who is a nonresident owner of real property may defend against a claim relating to that property without personally appearing by (1) submitting written declarations to serve as evidence supporting their defense, (2) allowing another individual to appear and participate on their behalf if that individual is serving without compensation and has appeared in small claims actions on behalf of others no more than four times during the calendar year, or (3) taking the action described in both (1) and (2).
(h) A party who is an owner of rental real property may appear and participate in a small claims action through a property agent under contract with the owner to manage the rental of that property, if (1) the owner has retained the property agent principally to manage the rental of that property and not principally to represent the owner in small claims court, and (2) the claim relates to the rental property.
(i) A party that is an association created to manage a common interest development, as defined in Section 4100 or in Sections 6528 and 6534 of the Civil Code, may appear and participate in a small claims action through an agent, a management company representative, or bookkeeper who appears on behalf of that association.
(j) At the hearing of a small claims action, the court shall require any individual who is appearing as a representative of a party under subdivisions (b) to (i), inclusive, to file a declaration stating (1) that the individual is authorized to appear for the party, and (2) the basis for that authorization. If the representative is appearing under subdivision (b), (c), (d), (h), or (i), the declaration also shall state that the individual is not employed solely to represent the party in small claims court. If the representative is appearing under subdivision (e), (f), or (g), the declaration also shall state that the representative is serving without compensation, and has appeared in small claims actions on behalf of others no more than four times during the calendar year.
(k) A spouse who sues or who is sued with their spouse may appear and participate on behalf of their spouse if (1) the claim is a joint claim, (2) the represented spouse has given their consent, and (3) the court determines that the interests of justice would be served.
(l) If the court determines that a party cannot properly present their claim or defense and needs assistance, the court may in its discretion allow another individual to assist that party.
(m) Nothing in this section shall operate or be construed to authorize an attorney to participate in a small claims action except as expressly provided in Section 116.530.