How to modify child support or spousal support in California

Sources last checked: 3 November 2026. The Cusp is not a law firm. Information only, not legal advice.

California divorce kitHow child support is calculatedSpousal support in CaliforniaLegal aid in California

The short version

In California you ask the court to change a support order by filing a Request for Order in your existing family law case. The court’s form is Request for Order (FL-300), shown on the Judicial Council page as effective July 1, 2025. For both child support and long-term spousal support, the California Courts Self-Help Guide says you also file an Income and Expense Declaration (FL-150), effective September 1, 2024. For child support, the guide says you can ask the judge to change support if things changed since the last order. For long-term spousal support, it says the court will only change an order if “something significant has changed since the court made the last order”.

Timing matters

  • Section 3651 of the Family Code says a support order may be “modified or terminated at any time as the court determines to be necessary”, with listed exceptions.
  • The same section says an order may not be changed for an amount that “accrued before the date of the filing of the notice of motion” to modify. In plain terms, the court generally cannot change what was already owed before you filed.
  • Section 3653 says a modifying order may be made “retroactive to the date of the filing of the notice of motion” or “to any subsequent date”. The Self-Help Guide puts it practically: ask as soon as your situation changes, because the court can only change the amount back to the day you filed.
  • Section 3653 has separate rules for unemployment and for military activation and deployment. We summarise none of the details here. Read the section if either applies.

What you file

  • Request for Order, FL-300. For child support the guide says to use item 3 on page 3 and item 9, “Facts to Support”, on page 4. For spousal support it says to use item 4 on page 3 and item 9. You can ask to change other orders, such as custody or child support, on the same form.
  • Income and Expense Declaration, FL-150. It asks how much money you earn and how you spend it. The guide says to attach proof of income from the past two months and not to attach last year’s tax return, but to bring a copy to the hearing.
  • Spousal or Domestic Partner Support Declaration Attachment, FL-157, for long-term spousal support. The guide calls it optional but helpful. If you do not use it, you need to explain the same factors in a separate document.
  • Supporting documents such as a letter from your employer or unemployment paperwork. The guide says to black out Social Security and account numbers.
  • If you and the other party agree: the guide says you can write up the agreement and turn it in for a judge to sign. It has separate pages for child support agreements and long-term spousal support agreements. If a Local Child Support Agency (LCSA) is part of your child support case, the guide says to use different instructions and that the LCSA must also approve any agreement.
  • Simplified option: the Judicial Council also lists Notice of Motion and Motion for Simplified Modification of Order for Child, Spousal, or Family Support (FL-390). Its page lists an effective date of January 1, 2003. We have not confirmed who can use it. Ask your court’s family law facilitator before choosing it.

What the law says about spousal support

  • Section 4320 lists what the court weighs when it orders spousal support. It says “the court shall consider all of the following circumstances”. They include “The ability of the supporting party to pay spousal support”, “The needs of each party based on the standard of living”, the length of the marriage and the age and health of the parties.
  • Section 3651(d) says spousal support cannot be changed if a written agreement, or an oral agreement made in open court, says that “spousal support is not subject to modification or termination”. Check your agreement and judgment for that kind of wording before you file.
  • Section 3590 says the support terms of an agreement are separate from its property terms, and a support order based on the agreement is made under the court’s power to order spousal support.
  • The Self-Help Guide says it uses “spousal support” to also mean domestic partner support.

Filing, service and hearing

  • Where: the guide says you need a family law court case. For a change to an existing order, you file in that case with the court clerk. Give the clerk the original and 2 copies. The clerk stamps the forms, writes a hearing date on the Request for Order, keeps the original and returns your copies.
  • Fee: the Self-Help Guide says “Pay a $60 fee” unless you have a fee waiver, and that there may be other fees. If the papers are the first you have filed in the case, it says there is a $435 to $450 “first paper” fee. If you cannot afford a fee, you can ask for a fee waiver. Confirm the current amount with your court clerk.
  • Serving the other side: the guide says you cannot serve the papers yourself. Another adult, 18 or over and not part of your case, must do it. Some situations require personal service rather than mail. When mail is allowed, the guide says the server must mail the papers “at least 16 court days plus 5 calendar days before your court date”, unless the court orders a different time. It gives a different rule for out-of-state parties that we did not read in full. See the guide’s page on serving a Request for Order.
  • Hearing: the guide says a judge decides your request at the hearing. Bring a copy of your latest tax return if you have one.

What we could not confirm

  • Whether California uses a named legal test such as “substantial change”. Section 3651 does not use those words. The Self-Help Guide says “things changed” for child support and “something significant” for spousal support. We did not read case law.
  • How child support is calculated. We did not read the guideline statutes (Family Code section 4050 onward). The guide points to a free online calculator and your county’s family law facilitator.
  • Who can use the simplified form FL-390, and its companion forms. We read only its listing page.
  • Revision dates beyond what the Judicial Council pages state. We read the “Effective” dates on those pages, not the PDFs. FL-157’s date was not checked.
  • Court-specific fees, local rules, e-filing, and the extra steps when the other party lives out of state. The fee figures are the guide’s statewide statement.
  • Cases where the LCSA is involved. The guide says the process is different. We did not read that page.
  • Whether a court kept the power to change spousal support in your case. That depends on your judgment and agreement, which we have not seen.
  • Tax effects of changing spousal support.

Before you file

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Sources