A party may want to prove that a potential defendant received notice or some written communication. Process service certainly satisfies that goal. However, a cheaper and just as reliable method is certified mail. A demand letter — does not itself — carry legal significance as such with a summons and complaint. When sending correspondence without such significant impacts, certified mail would effectively accomplish the goal of proving receipt.
“Process Service” is the delivery of documents — normally in-person — by an individual authorized by statute or common law to do so. Most often, any person over the age of 18 and not a party to the case. However, sometimes regulations provide additional requirements. Process Service is proven by the affidavit of the process server.
In legal matters, process service accomplishes the goal of proving an individual’s notice and receipt of a Complaint that has or will be filed against them and their requirements to appear and respond (Summons) to the court. Once the process is conducted (a person is “served”), the clock for any “Answer” (formal response to the allegations in a complaint) requirements begins. Statutory requirements for Answers vary from jurisdiction to jurisdiction, frequently with considerations for where and how the process is served (E.g., in-state or out-of-state service, notice by publication)
Washington courts recognize several methods of effective process service: “To the defendant personally, or by leaving a copy of the summons at the house of his or her usual abode with some person of suitable age and discretion then resident therein.” If personal service or secondary service cannot be reasonably accomplished, Washington law permits mail or public notice process, provided attempts to more direct service can be proven or are unavailable.
A distinguishing characteristic of documents requiring process service is that those, like a complaint and summons, carry significant legal ramifications for failure to comply or respond: Loss of legal rights, fines, and even imprisonment for failure to appear.