Maryland Certificate of Service — First Class Mail is a document used to certify that a document was securely delivered by U.S. Postal Service first class mail. The Maryland Certificate of Service is typically used in legal matters by attorneys or court clerks when sending documents to parties or entities. It is required to be completed when filing a document with the Maryland court system. There are three types of Maryland Certificate of Service — First Class Mail: Standard Certificate of Service, Affidavit of Service, and Certificate of Service by Mail. The Standard Certificate of Service is used for documents sent to individuals or entities located within Maryland. The Affidavit of Service is used for documents sent to individuals or entities outside of Maryland. The Certificate of Service by Mail is used for documents sent to individuals or entities located outside of Maryland but within the United States.