How To Write A Formal Letter On Behalf Of Someone . In addition to this signature line, the individual must put the name of the person on whose behalf he or she is signing the letter above or below the line with the “p.p.” designation. Start with the salutation, dear followed by the person's name, title and a comma. Sample of Authorization Letter Template to Act on Behalf from authorizationletter.net Make sure that you will look into all the areas of the authorization letter to act on behalf. Leave one line and write the date. Mention if any restrictions on the.