Legal Question in Civil Litigation in California

It means the defendant is saying you don't have to formally serve him. Usually when a defendant files this type of waiver he has received the summons and complaint by a means that does not qualify as proper service but has decided not to make the plaintiff jump through all the hoops proper service requires.

Service of process is normally what subjects a defendant to the court's authority. It also starts the clock on the defendant's duty to answer or bring a motion attacking the complaint. A defendant who waives service thereby submits to the court's authority and agrees to respond to the complaint just as if he had been served. Aside from the fact that you didn't actually serve him, the case will proceed exactly as it would have if the defendant had been served on the date he signed the waiver.

Note to other readers: the waiver of service is a standard form used in federal court. California state courts have a similar document called a notice and acknowledgment of receipt. There are some differences between the two procedures, but they serve the same purpose.

There is a mistake in my prior answer. I wrote that "the case will proceed exactly as it would have if the defendant had been served on the date he signed the waiver." It will actually proceed as it would have if the defendant had been served when the plaintiff sent the request for waiver, not when the defendant signed it.

The defendant's time to respond in a California state court would begin when he signs a notice and acknowledgment of receipt, not when it was sent to him. This is one of the differences I mentioned previously between the state and federal procedures.