Joint fiduciaries
Under such regulations as the Secretary may prescribe, a return made by one of two or more joint fiduciaries shall be sufficient compliance with the requirements of this section. A return made pursuant to this paragraph shall contain a statement that the fiduciary has sufficient knowledge of the affairs of the person for whom the return is made to enable him to make the return, and that the return is, to the best of his knowledge and belief, true and correct.