How to Modify Child Support in California
Reviewed by DocDraft Legal Team · California · Last updated September 21, 2026
In California, a child support modification is a court order changing the amount of an existing child support order, and unlike many states California sets no fixed percentage you must clear to ask a court, you simply show that circumstances have changed since the last order (Cal. Family Code 3651). Child support in California is set by a statewide guideline formula tied to each parent's income and time with the child (Cal. Family Code 4055), so a change in income, a job loss, or a new parenting schedule can make the current amount too high or too low. You can ask for a change in two ways. You can file a Request for Order (Form FL-300) with the superior court that handles your case, or, if the local child support agency manages your case, you can ask that agency for a review. The agency generally pursues a modification when the guideline amount would change by at least 20 percent or 50 dollars, whichever is less. A change takes effect only back to the date you file your request, not to when your circumstances changed, so support that already came due cannot be reduced (Cal. Family Code 3653). You can also ask for a review about every three years. Keep paying your current order until the court changes it. Attorney review of your filing is available through DocDraft.
Find out where you stand in California
Where are you with changing your child support order?
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How do I modify child support in California?
File a Request for Order (Form FL-300) with the superior court that issued your order, or ask the local child support agency to review it. You must show that circumstances have changed since the last order; California sets no fixed percentage for a court request (Cal. Family Code 3651).
How much does income have to change to modify child support in California?
For a court request, California requires no fixed percentage, only a real change in circumstances since the last order (Cal. Family Code 3651). The local child support agency generally pursues a modification when the guideline amount would change by at least 20 percent or 50 dollars, whichever is less.
How far back can a child support change go in California?
A modification can be made retroactive only to the date you file your Request for Order, not to when your circumstances changed (Cal. Family Code 3653). Support that already came due cannot be reduced, so filing promptly protects you. Keep paying the current order until a judge changes it.
Which court handles child support modifications in California?
The superior court in the county where your existing order is filed handles modifications, usually through the family law division. If the local child support agency manages your case, you can also ask that agency to review and adjust the order without a full court hearing. Both paths use the state guideline.
California child support modification at a glance
In California, you can change an existing child support order by showing that circumstances have changed since the order was made, and there is no fixed percentage you must clear to ask a court (Cal. Family Code 3651). Support is set by a statewide guideline tied to income and parenting time (Cal. Family Code 4055), so a change in either parent's income or the custody schedule can justify a new amount. You file a Request for Order (Form FL-300) with the superior court, or ask the local child support agency for a review; the agency generally acts when the guideline amount would change by at least 20 percent or 50 dollars, whichever is less. A change applies back only to the date you file, so support that already came due cannot be reduced (Cal. Family Code 3653).
Lowering a California order after a pay cut
Suppose you have a California child support order set two years ago when you earned more, and your hours were just cut. Because California requires no fixed percentage to ask a court, you complete a Request for Order (Form FL-300) with an Income and Expense Declaration showing your lower pay, and file it with the superior court that issued your order. You serve the other parent and get a hearing date. Because a change applies back only to your filing date (Cal. Family Code 3653), you file right away rather than waiting, and you keep paying the current amount until the judge rules. At the hearing the judge recalculates support under the guideline (Cal. Family Code 4055) and signs a lower order effective from your filing date. Attorney review of your filing is available through DocDraft.
Relevant Laws
Cal. Family Code 3651 (modification of a support order)
Provides that a support order may be modified or terminated at any time as the court determines to be necessary, and sets the framework for changing an existing child support order in California without a fixed percentage trigger.
Cal. Family Code 3653 (effective date of a modification)
Provides that an order modifying or terminating a support order may be made retroactive to the date of the filing of the notice of motion or order to show cause to modify, or to a later date, so a change cannot reach earlier support.
Cal. Family Code 4055 (statewide guideline formula)
Sets out California's statewide uniform guideline formula for calculating child support based on each parent's net disposable income and the time each parent has primary physical responsibility for the children.
California Courts self-help: change a child support order
The Judicial Council self-help center explains how to request a change to a child support order, which forms to use including the Request for Order (Form FL-300), and how to serve the other parent.
Regional Variances
California child support modification rules at a glance
Qualifying threshold
California sets no fixed percentage for a court request; you show a change in circumstances since the last order (Cal. Family Code 3651). The local child support agency generally acts when the guideline amount would change by at least 20 percent or 50 dollars, whichever is less.
Where to file
The superior court in the county handling your existing order, usually the family law division. If the local child support agency manages your case, you can ask it to review and adjust the order without a full court hearing.
Modification form
Form FL-300, the Request for Order, with an Income and Expense Declaration (Form FL-150). A simplified modification can sometimes use Form FL-390. Forms are free through the California Courts self-help site.
Retroactivity
A modification can date back only to the date you file your request, not to when circumstances changed (Cal. Family Code 3653). Support that already came due cannot be reduced.
Periodic review
If the local child support agency handles your case, you can generally request a review about every three years without showing a change, and sooner when a substantial change occurs.
Suggested Compliance Checklist
Gather proof of your changed circumstances
Before you file days after startingCollect current pay stubs, tax returns, and proof of the change (job loss, income change, or a new parenting schedule), and estimate the new guideline amount (Cal. Family Code 4055). Attorney review of your filing is available through DocDraft.
Complete the Request for Order (FL-300)
As soon as your circumstances change days after startingFill out Form FL-300 asking to change child support, describe the changed circumstances, and attach an Income and Expense Declaration (Form FL-150). Use the free California Courts self-help forms and instructions.
File with the superior court
Promptly (the change dates back to filing) days after startingFile your FL-300 with the superior court clerk and pay the fee, or request a fee waiver (Form FW-001). Because a change applies back only to your filing date, file promptly (Cal. Family Code 3653).
Serve the other parent
Before the hearing deadline days after startingHave an adult who is not you serve the other parent with your filed papers, then file the proof of service. Proper service is required for the judge to change the order at the hearing.
Consider an agency review
Anytime your case is with the agency days after startingIf the local child support agency manages your case, ask it to review your order. The agency generally acts when the guideline amount would change by at least 20 percent or 50 dollars, whichever is less.
Attend the hearing and get the new order
On your hearing date days after startingGo to the hearing with your income proof, let the judge recalculate support under the guideline, and get the signed order effective back to your filing date. Keep paying the current order until then.
| Task | Description | Document | Days after starting |
|---|---|---|---|
| Gather proof of your changed circumstances | Collect current pay stubs, tax returns, and proof of the change (job loss, income change, or a new parenting schedule), and estimate the new guideline amount (Cal. Family Code 4055). Attorney review of your filing is available through DocDraft. | - | Before you file |
| Complete the Request for Order (FL-300) | Fill out Form FL-300 asking to change child support, describe the changed circumstances, and attach an Income and Expense Declaration (Form FL-150). Use the free California Courts self-help forms and instructions. | - | As soon as your circumstances change |
| File with the superior court | File your FL-300 with the superior court clerk and pay the fee, or request a fee waiver (Form FW-001). Because a change applies back only to your filing date, file promptly (Cal. Family Code 3653). | - | Promptly (the change dates back to filing) |
| Serve the other parent | Have an adult who is not you serve the other parent with your filed papers, then file the proof of service. Proper service is required for the judge to change the order at the hearing. | - | Before the hearing deadline |
| Consider an agency review | If the local child support agency manages your case, ask it to review your order. The agency generally acts when the guideline amount would change by at least 20 percent or 50 dollars, whichever is less. | - | Anytime your case is with the agency |
| Attend the hearing and get the new order | Go to the hearing with your income proof, let the judge recalculate support under the guideline, and get the signed order effective back to your filing date. Keep paying the current order until then. | - | On your hearing date |
Frequently Asked Questions
A real, involuntary income drop can support a modification, but you must file a Request for Order to change the amount; support keeps accruing at the old rate until the court acts (Cal. Family Code 3653). A judge may consider whether you are earning what you reasonably could. Do not simply stop paying.
No. Either parent can file a Request for Order on their own, and the other parent is served and can respond. If both parents agree on a new amount, they can submit a written stipulation for a judge to approve. The judge still checks it against the guideline (Cal. Family Code 4055).
After you file Form FL-300, the court sets a hearing, often several weeks to a few months out depending on the county. An uncontested change or a local child support agency review can be faster. Because the change dates back only to your filing, filing promptly protects you (Cal. Family Code 3653).
Yes. If the local child support agency manages your case, you can ask it to review your order. The agency generally pursues a modification when the guideline amount would change by at least 20 percent or 50 dollars, whichever is less, and can take the matter to court if needed.
You can ask for a review whenever a substantial change in circumstances occurs, and if the local child support agency handles your case you can generally request a review about every three years even without a change, under federal rules. There is no limit on filing when circumstances genuinely change.
A modification changes support only from your filing date forward (Cal. Family Code 3653). Support that already came due, called arrears, cannot be reduced or erased by a modification, and it continues to accrue interest. Keep paying your current order to avoid building arrears while your request is pending.
Filing a Request for Order in superior court carries the standard family law filing fee, but you can ask the court to waive it with a fee waiver (Form FW-001) if you cannot afford it. A review through the local child support agency does not charge you a fee.
You start with Form FL-300, the Request for Order, and attach a current Income and Expense Declaration (Form FL-150). A simplified modification of a support order can sometimes use Form FL-390. The California Courts self-help website provides these forms and instructions at no charge.
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