Cal. Civ. Proc. Code § 1250.250
(b) The holder of a lien that secures a special assessment or a bond representing the special assessment shall be named as a defendant, regardless of the nature of the special assessment and the manner of collection of the special assessment. The holder of the lien may, instead of an answer, certify to the court within 30 days after service of the summons and complaint on the holder all of the following information: