If you don’t know how to sign a letter on behalf of someone else, you can start by using p.p. It stands for per procurationem. It is legally secure and shows that you represent someone else in your letter writing.

The legal convention is to include the initials, "p.p.," which stand for the Latin phrase, "per procurationem," meaning "to take care of something," before the employee's signature. Procuration of correspondence means to sign it on someone else's behalf; a common alternative used for form letters is to use a signature stamp.