Washington Confirmation of Service is a method of serving legal documents to an opposing party in a lawsuit. This type of service is required in all civil cases in Washington state. The Confirmation of Service is a document filed with the court that states that the opposing party was properly served the legal documents. There are two types of Washington Confirmation of Service: personal service and substituted service. Personal service requires documents to be served directly to the opposing party by an authorized messenger such as a sheriff or private process server. Substituted service arises when personal service is unsuccessful. The documents are then served on someone at the opposing party's residence or place of business, or by postal mail with a return receipt requested.