Washington Return of Service is a legal document that is used to serve legal notice to the person or entity being sued. It is a form signed by a process server that is filed with the court and states that the defendant was personally served with the legal documents. The document serves as proof that the defendant was notified of the lawsuit. The two types of Washington Return of Service are Personal Service and Substituted Service. Personal Service requires the process server to hand the documents to the defendant in person. Substituted Service allows the process server to serve the documents to someone who lives with the defendant, or to post them by mail.