Joinder in California family law is the procedure that adds a third party to a divorce, legal separation, or parentage case so the court’s orders can reach them. You use it when someone outside the marriage or parentage has a stake the court needs to resolve — an ownership interest in community property, control over a retirement account, or a claim to custody or visitation. Once joined, that person or entity is bound by whatever the court decides on the specific issue that brought them in.
When You Need to File a Joinder
Joinder comes up whenever property, debt, or a parenting issue can’t be fully resolved between just the two spouses or parents.
A business partner is the classic property example. If community property includes a stake in a business, the co-owner may need to be joined so the court can value and divide the community share without leaving the partner free to contest it later. The same logic covers trustees. When community assets sit inside a family trust, joining the trustee gives the court authority over those assets.
Custody and visitation is the other common trigger. California allows courts to grant reasonable visitation to grandparents during a family law proceeding when it serves the child’s best interest, with a similar provision for stepparents.1Justia. California Family Code Sections 3100-3105 A grandparent or stepparent seeking visitation typically joins the existing case rather than filing something separate. The Judicial Council’s own description of the joinder motion form specifically names grandparents and stepparents seeking custody or visitation as a common use.2California Courts. Notice of Motion and Declaration for Joinder (FL-371)
Retirement Plans and the ERISA Line
Dividing a retirement account almost always involves joinder, but not every plan gets joined the same way, and getting this wrong can cost months.
California Family Code Section 2060 requires the clerk to enter a joinder order for any employee benefit plan in which either spouse claims a divisible interest. A court order dividing retirement funds is not enforceable against the plan unless the plan has been formally joined.3California Legislative Information. California Family Code Division 6, Part 1, Chapter 6, Article 1 Government pensions sit squarely here: CalPERS, CalSTRS, University of California Retirement System, and county or public school retirement plans all require joinder before a California court can divide them.4Superior Court of California, County of Santa Clara. How to Request Joinder of Employee Benefit Plan
Most private-sector retirement plans, including 401(k)s, traditional pensions, and profit-sharing plans at private companies, are governed by the federal Employee Retirement Income Security Act. California Family Code Section 2337(d)(1) specifically exempts these plans from the state joinder requirement.5California Legislative Information. California Family Code FAM Section 2337 An ERISA plan is divided through a Qualified Domestic Relations Order instead. As long as the QDRO meets federal requirements, the plan administrator must honor it whether or not the plan was ever joined. If you aren’t sure which category a plan falls into, the Summary Plan Description will say, and the plan administrator can confirm.
The Forms You’ll Need
California uses specific Judicial Council forms, and the set changes depending on whether you’re joining a person or a retirement plan.
Joining a Person, Business Partner, or Trustee
Three forms:
- Notice of Motion and Declaration for Joinder (FL-371) — the motion asking the judge to add the third party.
- Pleading on Joinder (FL-370 or FL-373) — the facts: who the third party is, what interest they hold, and what you want the court to order.
- Summons for Joinder (FL-375) — issued once the judge signs the order.6Judicial Branch of California. California Rules of Court Rule 5.24 – Joinder of Persons Claiming Interest
Joining an Employee Benefit Plan
The plan process is simpler in one respect: no judge’s approval up front. You file the Request for Joinder of Employee Benefit Plan and Order (FL-372), and the clerk enters the joinder order directly.7California Courts. Request for Joinder of Employee Benefit Plan Order (FL-372) You also file the Pleading on Joinder—Employee Benefit Plan (FL-370), which tells the plan administrator what’s being claimed.8California Courts. Pleading on Joinder—Employees Benefit Plan (FL-370)
Whichever set you’re using, gather the full legal name and current address of the person or plan administrator before you file. For a plan, you’ll also need the plan name, plan number, and administrator’s contact information, which appear on the employee’s benefits statements. The employee spouse must supply this information within 30 days of a written request.9Justia. California Family Code 2060-2065 – Joinder of Plan
Filing, Fees, and Service
File your forms with the court clerk in the county where your case is pending. The filing fee for a family law motion is $60 as of 2026.10Judicial Branch of California. Statewide Civil Fee Schedule Effective 01-01-2026 If you can’t afford the fee, use form FW-001 to request a waiver.11California Courts. Request to Waive Court Fees
For a person or entity, a judge must review the motion and grant permission before joinder takes effect. Once the judge signs, the court directs issuance of the FL-375 summons.6Judicial Branch of California. California Rules of Court Rule 5.24 – Joinder of Persons Claiming Interest For a retirement plan, the clerk enters the order without a hearing.
Then you serve the joined party. An adult who isn’t involved in the case, or a professional process server, personally delivers the paperwork. For a retirement plan, the service packet includes the pleading on joinder, the request and order, the summons, and a blank notice of appearance form.9Justia. California Family Code 2060-2065 – Joinder of Plan For a person, the packet includes the FL-371 motion, the pleading, the order, and the summons.
The server completes a Proof of Service, and you file it with the court. That filing establishes the court’s jurisdiction over the joined party for the issues raised in the pleading.
After the Joined Party Is Served
The joined party has 30 days from the date of service to respond.12Judicial Branch of California. California Rules of Court Title 5 – Family and Juvenile Rules What that response looks like depends on who was served.
A retirement plan files a notice of appearance rather than a full answer. It isn’t required to file a substantive response and pays no filing fee. If the plan files only the notice of appearance, every factual statement and request in your pleading is automatically treated as disputed.9Justia. California Family Code 2060-2065 – Joinder of Plan If the plan doesn’t respond at all by the deadline, you can ask the clerk to enter a default.
A person or entity files a response to the joinder pleading much like an answer to a complaint. Once joined, they can conduct discovery, present evidence, and appear at hearings, but only on the specific issue that brought them in. A business partner joined over the value of a company has no standing on child support or parenting time. The general rules for civil actions govern joinder proceedings unless the court orders otherwise.12Judicial Branch of California. California Rules of Court Title 5 – Family and Juvenile Rules
Whatever the court decides on the joined issue binds the joined party directly. That’s what joinder buys you: a visitation schedule involving a grandparent, or an order telling a plan administrator how to divide a pension, carries the same legal weight against the third party as any order between the original spouses.