Cal. Family Code § 4065

(a) Unless prohibited by applicable federal law, the parties may stipulate to a child support amount subject to approval of the court. However, the court shall not approve a stipulated agreement for child support below the guideline formula amount unless the parties declare all of the following: (1) They are fully informed of their rights concerning child support. (2) The order is being agreed to without coercion or duress. (3) The agreement is in the best interests of the children involved. (4) The needs of the children will be adequately met by the stipulated amount. (5) The right to support has not been assigned to the county pursuant to Section 11477 of the Welfare and Institutions Code and no public assistance application is pending. (b) The parties may, by stipulation, require the child support obligor to designate an account for the purpose of paying the child support obligation by electronic funds transfer pursuant to Section 4508. (c) A stipulated agreement of child support is not valid unless the local child support agency has joined in the stipulation by signing it in any case in which the local child support agency is providing services pursuant to Section 17400. The local child support agency shall not stipulate to a child support order below the guideline amount if the children are receiving assistance under the CalWORKs program, if an application for public assistance is pending, or if the parent receiving support has not consented to the order. (d) If the parties to a stipulated agreement stipulate to a child support order below the amount established by the statewide uniform guideline, no change of circumstances need be demonstrated to obtain a modification of the child support order to the applicable guideline level or above.