October 2026

Serve the papers right. Then prove it. That second part trips up more people than the first. A defective proof of service can delay your case and block a default request. This guide covers what a proof of service is, who can sign one, and how to fill out POS-010 line by line. No theory. Just what works. What Is a Proof of Service? A proof of service is a signed statement telling the court who served what, on whom, when, where, and how. Simple concept. Heavy weight. Without it, the court has no record that your defendant was served. No valid service, no default. And if the proof doesn’t establish valid service, your case stalls. Picture this. A plaintiff waits out the response deadline and files for default. The judge rejects it. The proof of service says “legal papers” instead of listing the summons and complaint. The case loses three weeks, maybe more. Don’t be that plaintiff. Who Can Sign a Proof of Service in California? The person who did the serving signs it. That person must be: A party to the case can’t serve the summons and complaint themselves. Here’s who can: The key requirement is that the server is not a party. If there’s any question about whether someone qualifies, use a neutral adult or a professional. Rookie mistake: the plaintiff serves the papers and signs the proof. That service doesn’t count, and you start over. A professional process server in California knows the rules, keeps detailed notes, and can testify if the defendant claims, “I never got anything.” Registered process servers must also include their registration information on the proof of service. Which Form Do You Need? POS-010 Explained POS-010 is the Judicial Council form for proof of service of summons. Use it to prove you served the summons, the complaint, and any other documents that went with them to start a lawsuit. Important: POS-010 is used to prove service of a summons and the documents served with it. Many other civil documents use POS-040, while electronic service uses POS-050. Don’t mix them up. You can find the official POS-010 form on the California Courts website. How to Fill Out POS-010, Step by Step Here’s how to fill out a proof of service on POS-010. Be specific everywhere. Pro tip: write it like you’re explaining it to a judge who wasn’t there. Plain facts. No guesses. Mistakes That Get a Proof of Service Rejected File It and Watch the Clock Serving isn’t enough. File the signed proof with the court. Don’t leave it in a folder. For most civil cases covered by California Rules of Court, rule 3.110, you must serve all named defendants and file proofs of service within 60 days after filing the complaint. Some case types follow different rules. Miss the deadline without an extension, and the court can order you to explain why it shouldn’t impose sanctions. Substituted service has its own timing. Under the applicable California rules, it’s generally complete 10 days after the required mailing. The defendant’s response deadline runs from there, based on the rules for your case. Check your local court rules too. When to Stop DIY-ing and Hire a Pro Hire help when: Pricing varies by location, number of attempts, urgency, and difficulty. Rush jobs and hard-to-find defendants cost more. A failed DIY attempt costs more still. Ranworks handles exactly these situations through its California process serving services, with clean proofs ready to file. FAQs Not Sure Your Service Will Hold Up? If you’re staring at POS-010 and something feels off, stop before you file. Don’t submit a questionable proof and hope it passes. Talk to Ranworks. We’ll tell you straight whether your service holds up, and we’ll handle it if it doesn’t. Contact Us today and get it right the first time.