36 CFR §1202.22

1. (a)Before a NARA employee or NARA contractor asks you to provide your social security number (SSN), he or she will ensure that the disclosure is required by Federal law or under a Federal law or regulation adopted before January 1, 1975.
2. (b)If you are asked to provide your SSN, the NARA employee or contractor must first inform you:
   1. (1)Whether the disclosure is mandatory or voluntary;
   2. (2)The statute or authority under which your SSN is solicited; and
   3. (3)How your SSN will be used.