California Code, Family Code - FAM § 4052.5

(a) The statewide uniform guideline, as required by federal regulations, shall apply in any case in which a child has more than two parents. The court shall apply the guideline by dividing child support obligations among the parents based on income and amount of time spent with the child by each parent, pursuant to Section 4053.

(b) Consistent with federal regulations, after calculating the amount of support owed by each parent under the guideline, the presumption that the guideline amount of support is correct may be rebutted if the court finds that the application of the guideline in that case would be unjust or inappropriate due to special circumstances, pursuant to Section 4057. If the court makes that finding, the court shall divide child support obligations among the parents in a manner that is just and appropriate based on income and amount of time spent with the child by each parent, applying the principles set forth in Section 4053 and this article.

(c) Nothing in this section shall be construed to require reprogramming of the California Child Support Enforcement System, a change to the statewide uniform guideline for determining child support set forth in Section 4055, or a revision by the Department of Child Support Services of its regulations, policies, procedures, forms, or training materials.