31 CFR 18.1 - Designation of First Assistants.
Except as provided in § 18.2, every office within the Department of the Treasury (including its bureaus) to which appointment is required to be made by the President with the advice and consent of the Senate (“PAS Office”) may have a First Assistant within the meaning of 5 U.S.C. 3345- 3349d.
(a) Where there is a position of principal deputy to the PAS Office, the principal deputy shall be the First Assistant.
(b) Where there is only one deputy position to the PAS Office, the official in that position shall be the First Assistant.
(c) Where neither paragraph (a) nor (b) of this section is applicable to the PAS Office, the Secretary of the Treasury may designate in writing the First Assistant.