31 CFR § 10.20 - Information to be furnished.
(a) To the Internal Revenue Service.
(1) A practitioner must, on a proper and lawful request by a duly authorized officer or employee of the Internal Revenue Service, promptly submit records or information in any matter before the Internal Revenue Service unless the practitioner believes in good faith and on reasonable grounds that the records or information are privileged.
(2) Where the requested records or information are not in the possession of, or subject to the control of, the practitioner or the practitioner's client, the practitioner must promptly notify the requesting Internal Revenue Service officer or employee and the practitioner must provide any information that the practitioner has regarding the identity of any person who the practitioner believes may have possession or control of the requested records or information. The practitioner must make reasonable inquiry of his or her client regarding the identity of any person who may have possession or control of the requested records or information, but the practitioner is not required to make inquiry of any other person or independently verify any information provided by the practitioner's client regarding the identity of such persons.
(3) When a proper and lawful request is made by a duly authorized officer or employee of the Internal Revenue Service, concerning an inquiry into an alleged violation of the regulations in this part, a practitioner must provide any information the practitioner has concerning the alleged violation and testify regarding this information in any proceeding instituted under this part, unless the practitioner believes in good faith and on reasonable grounds that the information is privileged.
(b) Interference with a proper and lawful request for records or information. A practitioner may not interfere, or attempt to interfere, with any proper and lawful effort by the Internal Revenue Service, its officers or employees, to obtain any record or information unless the practitioner believes in good faith and on reasonable grounds that the record or information is privileged.
(c) Effective/applicability date. This section is applicable beginning August 2, 2011.