Cal. Civ. Code § 8-3-208

(a) An aggrieved person may, not later than one year after an alleged discriminatory housing practice has occurred or terminated, file a complaint with the administrator alleging such discriminatory housing practice. The administrator, on the administrator’s own initiative, may also file such a complaint. Complaints shall be in writing and under oath and shall contain such information and be in such form as the administrator requires. Upon the filing of a complaint under this subsection, the administrator shall serve notice upon the aggrieved person acknowledging the filing and advising the aggrieved person of procedural time limits and the choice of forums provided under this article.
(b) The administrator shall, not later than ten days after the filing of a complaint or the identification of an additional respondent under subsection (d) of this Code section, serve on the respondent a notice identifying the alleged discriminatory housing practice and advising such respondent of the procedural rights and obligations under this article, together with a copy of the original complaint. Each respondent may file, not later than ten days after receipt of notice from the administrator, an answer to the complaint.
(c) Complaints and answers shall be verified and may be reasonably and fairly amended at any time.
(d) A person who is not named as a respondent in a complaint, but who is identified as a respondent in the course of an investigation, may be joined as an additional or substitute respondent upon written notice to such person from the administrator as provided in subsection (b) of this Code section. In addition to meeting the requirements of subsection (b) of this Code section, the notice shall explain the basis for the administrator’s belief that such person is properly joined as a respondent.