Child Support in Redwood City and San Mateo County, California

San Mateo County occupies much of the Peninsula between San Francisco and Santa Clara County, with Daly City, San Mateo, Redwood City, South San Francisco, and San Bruno among its largest cities. Families throughout the county bring child support matters to the Superior Court of California, County of San Mateo, whose Family Law Division sits at the Hall of Justice and Records (the court's Southern Branch) at 400 County Center in Redwood City, and to the county's Department of Child Support Services (DCSS), the local agency that opens and enforces support cases.

Like the rest of California, San Mateo County determines child support using the state's uniform guideline formula under Family Code section 4055. The formula is built from both parents' net disposable incomes and the timeshare, the amount of time the child spends with each parent, producing a figure the law treats as presumptively correct.

Two paths lead to a support order in San Mateo County. A parent already 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) at the Family Law Division. Or San Mateo County DCSS, part of the statewide Department of Child Support Services, can open a case directly to establish parentage and set up support without either parent filing their own family law case. The Judicial Council forms themselves don't change from county to county; the local piece is which courthouse and agency office you deal with, and in San Mateo County that's the Hall of Justice and Records and DCSS's office in Redwood City.

Before filing, it can help to run the numbers. Our free California child support calculator is available for that. If both parents already agree on a number, they can submit a written stipulation for a judge to sign instead of going through a hearing.

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 San Mateo 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 San Mateo County

Child support in San Mateo County is handled through the Superior Court of California, County of San Mateo, 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 and local agency office details change over time, confirm current details using the official California Courts court finder:

Find the San Mateo County Superior Court (official California Courts finder)

Local notes for San Mateo County

San Mateo County's family law matters, including Request for Order and child support filings, are heard at the Family Law Division of the Hall of Justice and Records, the court's Southern Branch at 400 County Center in Redwood City; confirm current hours and any procedural updates on the court's own website before filing. Attorneys are required to e-file family law documents through the Odyssey eFileCA system, and self-represented parents can also e-file several family law forms, including the Request for Order and Income and Expense Declaration, through the court's Odyssey Guide & File tool rather than filing in person.

San Mateo County's Department of Child Support Services runs its own office separate from the court system and offers free help to open a child support case, establish parentage, and enforce an existing order. The court's Self-Help Center and Family Law Facilitator office assists parents representing themselves with completing Form FL-150 and related paperwork by appointment, and can explain the general process, though staff cannot give legal advice about your specific case. Given the high cost of living on the Peninsula, precise and complete income reporting on that declaration is especially important, since it's what drives the guideline result.

As under California law statewide, child support in San Mateo 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 ask the court to modify support later if income or the parenting timeshare changes.

Official child support resources in San Mateo County

Child support cases that are part of a divorce, parentage, or custody matter in San Mateo County are filed with the Family Law Division at the Hall of Justice and Records, the Superior Court's Southern Branch at 400 County Center in Redwood City. That is where a Request for Order (Form FL-300) and Income and Expense Declaration (Form FL-150) are filed and where a family law hearing would take place.

San Mateo County's Department of Child Support Services (DCSS), part of the statewide California Department of Child Support Services, is the local agency that can open a child support case on its own, separate from any court filing. DCSS offers its services free of charge, including establishing parentage and enforcing an existing order, and its office is also in Redwood City.

Parents representing themselves can get free procedural help from the Superior Court's Self-Help Center and Family Law Facilitator office, which assists by appointment with forms like FL-150 and can explain the general process, though staff cannot give legal advice about a specific case. Attorneys must e-file family law documents through the court's Odyssey eFileCA system, and self-represented parents can also e-file several family law forms, including the Request for Order and Income and Expense Declaration, through the court's Odyssey Guide & File tool instead of filing in person.

• San Mateo County Department of Child Support Services
• Superior Court of California, County of San Mateo: Family Law Division
• Superior Court of California, County of San Mateo: Self-Help Center / Family Law Facilitator
• Superior Court of California, County of San Mateo: Child Support (Self-Help)

Local details reviewed July 2026. Offices and locations can change, so confirm with the official sites above before you file.

San Mateo County Child Support FAQs