26 U.S. Code § 6103 - Confidentiality and disclosure of returns and return information
(f)Disclosure to Committees of Congress
(3)Other committees
Pursuant to an action by, and upon written request by the chairman of, a committee of the Senateor the House of Representatives (other than a committee specified in paragraph (1)) specially authorized to inspect any
return or
return information by a resolution of the Senateor the House of Representatives or, in the case of a joint committee (other than the joint committee specified in paragraph (1)) by concurrent resolution, the Secretary shall furnish such committee, or a duly authorized and designated subcommittee thereof, sitting in closed executive session, with any
return or
return information which such resolution authorizes the committee or subcommittee to inspect.
Any resolution described in this paragraph shall specify the purpose for which the return or return information is to be furnished and that such information cannot reasonably be obtained from any other source.