California Proof of Service by Mail — Governmental is a legally binding process that is used to formally deliver documents to an individual or entity. It is typically used when an individual is required to be formally served with legal papers, such as a summons, complaint, subpoena, or other legal document. The process requires a mailing of the papers, which must be done through the United States Postal Service, along with the completion of a signed "Proof of Service" form. There are two types of California Proof of Service by Mail — Governmental: Regular Mail and Certified Mail. The Regular Mail option is the most common and is used when the individual or entity is known and can be expected to accept service. It requires the documents to be placed in an envelope addressed to the individual or entity and mailed via the United States Postal Service. The Certified Mail option is more formal than Regular Mail and is used when the individual or entity is uncertain or unwilling to accept service. It requires the documents to be placed in an envelope addressed to the individual or entity and mailed via the United States Postal Service, with a green “Certified Mail” sticker affixed to the envelope. It also requires the completion of a green “Certified Mail” form to be completed and returned to the sender as proof of service.