California Code, Family Code - FAM § 3761

(b)(1) The application shall state that the party or local child support agency seeking the assignment order has given the obligor a written notice of the intent to seek a health insurance coverage assignment order in the event of a default in instituting coverage required by court order on behalf of the parties' child and that the notice was transmitted by first-class mail, postage prepaid, or personally served at least 15 days before the date of the filing of the application for the order. The written notice of the intent to seek an assignment order required by this subdivision may be given at the time of filing a petition or complaint for support or at any later time, but shall be given at least 15 days before the date of filing the application under this section. The obligor may at any time waive the written notice required by this subdivision.

(2) The party or local child support agency seeking the assignment order shall file a certificate of service showing the method and date of service of the order and the statements required under Section 3772 upon the employer or provider of health insurance.