The most formal way of signing a letter on behalf of your boss is by using the designation p.p., an abbreviation of the Latin phrase “per procurationem.” Simply put, the initials p.p. before your name indicates that your boss has granted you the authority to make the correspondence on their behalf.

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. It's acceptable to either type or write, "p.p." in front of your own signature, above the printed name of the sender.