The officers and employees of the Internal Revenue Service whom the Commissioner has designated are authorized to administer such oaths or affirmations and to certify to such papers as may be necessary under the internal revenue laws or regulations issued thereunder, except that the authority to certify shall not be construed as applying to those papers or documents the certification of which is authorized by separate order or directive.
26 C.F.R. §301.7622-1
Sec. 7805, Internal Revenue Code of 1954, 68A Stat. 917; 26 U.S.C. 7805