California Certificate Of Service is a legal document used to certify that legal documents have been properly served on an opposing party or on a third party. This document is required by the California Rules of Court as a proof of service in the Superior Court system. There are two types of California Certificate Of Service: Certificate of Service by Mail and Certificate of Service by Personal Delivery. Certificate of Service by Mail requires that the document be sent to the party through the United States Postal Service and that the document be signed and dated by the person who sent it. Certificate of Service by Personal Delivery requires that the document be personally delivered to the party and that the document be signed by the party and dated.