20 C.F.R. § 401.85
(b) Specific systems of records exempted.
(1) Those systems of records listed in paragraph (b)(2) of this section are exempt from the following provisions of the Act and this part:
(2) The following systems of records are exempt from those provisions of the Privacy Act and this part listed in paragraph (b)(1) of this section:
(ii) Pursuant to subsection (k)(2) of the Privacy Act:
(iii) Pursuant to subsection (k)(5) of the Privacy Act:
(c) Notification of or access to records in exempt systems of records.
(2) We will grant you notification of or access to a record in an exempt system but only to the extent such notification or access would not reveal the identity of a source who furnished the record to us under an express promise, and prior to September 27, 1975, an implied promise, that his or her identity would be held in confidence, if: