Any oath or affirmation required or authorized under any internal revenue law or under any regulations made thereunder may be administered by any person authorized to administer oaths for general purposes by the law of the United States, or of any State or possession of the United States, or of the District of Columbia, wherein such oath or affirmation is administered. This subsection shall not be construed as an exclusive enumeration of the persons who may administer such oaths or affirmations.
26 U.S. Code § 7622. Authority to administer oaths and certify
(a) Internal revenue personnel