26 U.S.C. § 6903: Notice of fiduciary relationship

(a) Rights and obligations of fiduciaryUpon notice to the Secretary that any person is acting for another person in a fiduciary capacity, such fiduciary shall assume the powers, rights, duties, and privileges of such other person in respect of a tax imposed by this title (except as otherwise specifically provided and except that the tax shall be collected from the estate of such other person), until notice is given that the fiduciary capacity has terminated. (b) Manner of noticeNotice under this section shall be given in accordance with regulations prescribed by the Secretary.