California Code, Family Code - FAM § 4061

(a) If there needs to be an apportionment of expenses pursuant to Section 4062, the expenses shall be divided in proportion to the parents' net incomes as adjusted pursuant to subdivisions (c) and (d), unless a party requests or the court finds on its own motion that expenses should be divided in a different manner.

(c) In cases when spousal support is or has been ordered to be paid by one parent to the other, for purposes of allocating additional expenses pursuant to Section 4062, the gross income of the parent paying spousal support shall be decreased by the amount of the spousal support paid and the gross income of the parent receiving the spousal support shall be increased by the amount of the spousal support received for as long as the spousal support order is in effect and is paid.

(d) For purposes of computing the adjusted net disposable income of the parent paying child support for allocating any additional expenses pursuant to Section 4062, the net disposable income of the parent paying child support shall be reduced by the amount of any basic child support ordered to be paid under subdivision (a) of Section 4055. However, the net disposable income of the parent receiving child support shall not be increased by any amount of child support received.

(e) This section shall be operative September 1, 2024.