Child Support in Contra Costa County, California

Contra Costa County, seated in Martinez and made up of communities like Concord, Richmond, Antioch, Walnut Creek, and San Ramon, handles child support matters through the Superior Court of California, County of Contra Costa, and the county's Local Child Support Agency. Families throughout the county's varied cities, from the industrial waterfront towns to the inland suburbs, use the same court system.

California sets child support the same way in Contra Costa County as it does everywhere else: through a statewide uniform guideline formula found in Family Code section 4055. The formula combines both parents' net disposable incomes with the timeshare, the percentage of time the child spends in each parent's care, into an amount the law presumes to be correct.

There are two ways a support order gets put in place here. A parent already involved in a divorce, parentage, or custody case can file a Request for Order (Form FL-300) with an Income and Expense Declaration (Form FL-150). Alternatively, the county's Local Child Support Agency, part of the statewide Department of Child Support Services, can open a case on its own to establish and enforce support. The forms are the same across California; the local piece is which courthouse and which agency office handle your case.

Before you file, it's worth checking roughly what to expect. Our free California Guideline Child Support Calculator at /tools/california-child-support-calculator uses the same income and timeshare inputs the court relies on. If both parents already agree on an amount, a written stipulation can be submitted for a judge's signature instead.

How child support is calculated in California

California sets child support with a statewide uniform guideline (Family Code section 4055) that applies the same way in Contra Costa County as everywhere else. The formula is based mainly on two things:

1. Both parents' net disposable incomes.
2. The percentage of time the child spends with each parent (the timeshare).

The guideline amount is presumed to be correct, and courts use a calculator to run the numbers. Because the result depends on accurate income, the Income and Expense Declaration (Form FL-150) you file is what drives your number.

Where child support cases are handled in Contra Costa County

Child support in Contra Costa County is handled through the Superior Court of California, County of Contra Costa, with the county seat in Martinez, and the county's Local Child Support Agency, which is part of the California Department of Child Support Services. There are two common paths:

1. Either parent files a Request for Order (Form FL-300) with an Income and Expense Declaration (Form FL-150) inside a divorce, parentage, or custody case.
2. The Local Child Support Agency opens a case to establish, collect, and enforce support, often at no cost to the parents.

Because courthouse locations and the local agency office change over time, confirm current details using the official California Courts court finder:

Find the Contra Costa County Superior Court (official California Courts finder)

Local notes for Contra Costa County

Contra Costa County directs family law cases to particular courthouse locations, so confirm which one applies to yours using the official California Courts court finder before filing. The county's Local Child Support Agency office is separate from the court system; find current details through the California Department of Child Support Services website.

The self-help center in Contra Costa County assists parents representing themselves with completing Form FL-150 and related documents and explains the general filing process, but staff cannot give legal advice specific to your case. Because the guideline number is driven directly by the income figures reported, completing that form accurately is the single biggest factor in the outcome.

As under California law statewide, child support in Contra Costa County generally continues until the child turns 18, or 19 if the child is still a full-time high school student living at home and not self-supporting. Either parent can request a modification later if income or the parenting timeshare changes meaningfully.

Contra Costa County Child Support FAQs