Code of Civil Procedure section 415.30
(a)
A summons may be served by mail as provided in this section. A copy of the summons and of the complaint shall be mailed (by first-class mail or airmail, postage prepaid) to the person to be served, together with two copies of the notice and acknowledgment provided for in subdivision (b) and a return envelope, postage prepaid, addressed to the sender.(b)
The notice specified in subdivision (a) shall be in substantially the following form:(c)
Service of a summons pursuant to this section is deemed complete on the date a written acknowledgement of receipt of summons is executed, if such acknowledgement thereafter is returned to the sender.(d)
If the person to whom a copy of the summons and of the complaint are mailed pursuant to this section fails to complete and return the acknowledgement form set forth in subdivision (b) within 20 days from the date of such mailing, the party to whom the summons was mailed shall be liable for reasonable expenses thereafter incurred in serving or attempting to serve the party by another method permitted by this chapter, and, except for good cause shown, the court in which the action is pending, upon motion, with or without notice, shall award the party such expenses whether or not he is otherwise entitled to recover his costs in the action.(e)
A notice or acknowledgment of receipt in form approved by the Judicial Council is deemed to comply with this section.
Source:
Section 415.30, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CCP§ionNum=415.30.
(accessed May 4, 2025).