36 CFR § 1202.22
Will NARA need my Social Security Number?
November 4, 2020
(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.
(b) If you are asked to provide your SSN, the NARA employee or contractor must first inform you:
(1) Whether the disclosure is mandatory or voluntary;
(2) The statute or authority under which your SSN is solicited; and
(3) How your SSN will be used.