How guideline child support works in California

Section 4055 sets out a formula that combines both parents' net disposable incomes, the percentage of time the higher earner has primary physical responsibility for the children, and a fraction that changes with total income and the number of children. You do not need to work the math by hand, but it helps to know which facts drive the result: income and timeshare.

Net disposable income starts with gross income from almost any source, including wages, self-employment income, commissions, bonuses, rental income and many benefits. Certain items are deducted, such as taxes, mandatory retirement contributions, health insurance premiums for the parent and children, and support actually paid for children from other relationships. A judge can sometimes use earning capacity instead of actual income when a parent is able and has the opportunity to work but does not.

The California Department of Child Support Services provides a free online Guideline Calculator. It asks for each parent's income, deductions, filing status and timeshare and produces an estimate. Courts and attorneys often use certified software that performs the same calculation. Because small changes in income or timeshare can change the result, enter accurate figures and keep the documents that support them, such as pay stubs and tax returns.

The estimate is a starting point. The judge decides the order based on the evidence, including each party's Income and Expense Declaration (form FL-150) or, in some cases, a Financial Statement (Simplified).

Family Code section 4062 adds certain costs on top of the base guideline amount. These are usually shared equally between the parents unless one parent asks for a different split in proportion to income.

Every county is served by a local child support agency. Its services are free and it can help establish parentage, open a support case, calculate and collect support, and ask the court to change an order. If a parent receives certain public assistance for the children, the agency is generally involved automatically. The agency's attorney appears in court but does not represent either parent, so each parent may still want independent legal advice. If the agency is involved, it typically needs to approve agreements about support.

Child support can be modified when circumstances change, for example a significant change in income, a job loss or a change in parenting time. A judge can generally make a change retroactive only to the date the request was filed, so it helps to file promptly instead of waiting. Informal agreements to pay a different amount that are never approved by the court can lead to arrears. Support usually continues until a child turns 18, or later in some cases, such as a full-time high school student who is not self-supporting.