It is established etiquette by the Joint Chiefs of Staff, United States Department of Defense, the U.S. Army, the U.S. Navy, and the U.S. Air Force that the closing “Respectfully yours” be reserved for the President of the United States (according to U.S. Army standards, this also extends to the first lady and the President_elect).
The Complimentary Close: It is a humble way of ending a letter. It is written in accordance with the salutation. The most generally used complimentary close are Yours faithfully, Yours sincerely, and Thanks & Regards. Signature and Writer’s Identification: It includes signature, name, and designation of the sender. It can also include other details like contact number, address etc. The signature is handwritten just above the name of the sender. Enclosures: Enclosures show the documents attached to the letter. The documents can be anything like cheque, draft, bills, receipts, invoices etc. It is listed one by one. Copy Circulation: It is needed when the copies of the letter are sent to other persons. It is denoted as C.C. PostScript: The sender can mention it when he wants to add something other than the message in the body of the letter. It is written as P.S.