How to change child support in California

The rule for changing support, the forms, and a ready letter to the agency.

Checked against official sources: Oct 25, 2026.

Short answer

To modify an order means to change the amount by a new order. When circumstances change, such as a big rise or drop in either parent's income or a change in custody or parenting time.

Agency review
Every 3 years if a parent asks (federal law)
First form
Request for Order (FL-300)

The rule for changing support in California

When circumstances change, such as a big rise or drop in either parent's income or a change in custody or parenting time. California law sets no fixed percentage. A change can only go back to the date you filed your request, so file quickly.

Law: Cal. Fam. Code 3651

Can I ask for a change? Check your situation

California's rule: When circumstances change, such as a big rise or drop in either parent's income or a change in custody or parenting time. California law sets no fixed percentage. A change can only go back to the date you filed your request, so file quickly.

Law: Cal. Fam. Code 3651

Until a new order is made, the current amount is still owed. A change can count only from the date the other parent gets notice of your request, so ask soon.

Law: 42 U.S.C. 666(a)(9)

How to ask in California: If you disagree with the other parent, file a Request for Order (FL-300) with an Income and Expense Declaration (FL-150). If you agree, file a written agreement for the judge to sign. If an LCSA handles your case, ask the LCSA for a review or follow the LCSA court instructions; the LCSA must approve any agreement.

Asking for a review in California

If you disagree with the other parent, file a Request for Order (FL-300) with an Income and Expense Declaration (FL-150). If you agree, file a written agreement for the judge to sign. If an LCSA handles your case, ask the LCSA for a review or follow the LCSA court instructions; the LCSA must approve any agreement.

Write to the child support agency to ask for a review: Ask the agency to review (change) your order

New rules in California

SB 343: from September 1, 2024, updated income bands in the formula, a new low-income adjustment tied to full-time minimum wage, add-on costs shared by net income, and child care reimbursed only if actually paid; from January 1, 2026, 'presumed income' was replaced by earning capacity based on specific factors, with more ways to set aside default orders (Judicial Council of California, 2025 AB 1058 Conference).

Law: Stats. 2023, ch. 213

Jail, prison and support

State guidelines may not treat time in jail or prison as choosing not to work, when support is set or changed.

Law: 45 CFR 302.56(c)(3)

In nearby states

Your next steps in California

  1. Read your current order

    Note the date it was made or last changed and the amount.

  2. Compare with the rule

    In California: When circumstances change, such as a big rise or drop in either parent's income or a change in custody or parenting time.

  3. Collect papers

    Papers that show the change make the request stronger.

  4. File the request

    Ask for a review with California Department of Child Support Services (DCSS) (1-866-901-3212) · Apply online

Where to get free help in California

Questions about changing support in California

When can child support be changed in California?

When circumstances change, such as a big rise or drop in either parent's income or a change in custody or parenting time. California law sets no fixed percentage. A change can only go back to the date you filed your request, so file quickly.

How do I ask to change child support in California?

If you disagree with the other parent, file a Request for Order (FL-300) with an Income and Expense Declaration (FL-150). If you agree, file a written agreement for the judge to sign. If an LCSA handles your case, ask the LCSA for a review or follow the LCSA court instructions; the LCSA must approve any agreement.

Keep reading about California

Sources

Sources

Last checked: Oct 25, 2026.

Federal sources