The formal delivery of court papers that gives a court power over the person sued - and the step whose failure undoes more judgments than any other.
Service of process is the formal act of delivering a summons and complaint to the person being sued. It is not a courtesy or a notification: it is the step that gives the court authority over that defendant, and it is grounded in constitutional due process. A court that never acquired that authority has entered a judgment it had no power to enter, which is why service is the first thing a lawyer checks when a client says they knew nothing about a case.
The permitted methods are set by rule and vary by court and by who is being served. Personal delivery to the individual is the strongest. Most systems also permit substituted service - leaving the papers with a suitable adult at the home or workplace and usually mailing a copy as well - and service on a business through a registered agent. Service by publication in a newspaper exists as a last resort where a defendant genuinely cannot be found, and it normally requires the court's permission and proof that a real search was made first.
Who may serve matters as much as how. In most courts a party to the case cannot serve the papers themselves; it must be a sheriff, marshal, professional process server or other adult who is not involved. The server then files a proof of service or affidavit, and that document is what the court relies on. "Sewer service" - a server who files a sworn proof for a delivery that never happened - is the mechanism behind a large share of default judgments in consumer debt cases, and it is a fraud on the court as well as on the defendant.
Defective service is generally raised early or lost. Most systems require the objection to be made at the defendant's first appearance, because participating in the case on the merits without objecting is usually treated as accepting the court's authority. Where a judgment has already been entered, defective service is the strongest ground for having it set aside - and in some circumstances a judgment entered without valid service can be attacked long after an ordinary challenge would be too late.
Two moments are worth advice. The first is when a judgment appears that you never knew about - wages reduced, an account frozen, a credit report entry for a case you never saw. Whether you were validly served is the first question and often the decisive one, and it turns on documents you can obtain from the court file. The second is when you are the one suing and the defendant is avoiding service, because the permission to serve another way has to be applied for properly or the resulting judgment is vulnerable to exactly the challenge above.
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