How To Write A Married Name In A Formal Letter . I have enclosed a copy of proof of my name change. Address the letter with a mr. and ms. if the wife so prefers: FREE 16+ Witness Letter Formats in PDF MS World from www.sampletemplates.com As it doesn’t identify a woman by her marital status. Address a married couple using “mr.” and “mrs.” followed by the shared last name. The company they work for, if you are writing a formal business letter.