This authorization letter appoints someone to act as the author's attorney-in-fact to represent them before the Social Security System. SSS Authorization Letter is a document for authorizing an individual on your behalf to transact with the Social Security System.You can sign and submit a written statement appointing the person, or use our standard form SSA-1696, Appointment of Representative. A student's national percentile rank (NPR) is the student's standing as compared to a large representative sample of students in the same grade.