26 CFR § 1.6063-1 - Signing of returns, statements, and other documents made by partnerships.
(a) In general. Returns, statements, and other documents required to be made by partnerships under the provisions of subtitle A or F of the Code, or the regulations thereunder, with respect to any tax imposed by subtitle A of the Code shall be signed by any one of the partners. However, with respect to the signing of powers of attorney, see paragraph (a)(2) of § 601.504 of this chapter (Statement of Procedural Rules).
(b) Evidence of authority to sign. A partner's signature on a return, statement, or other document made by or for a partnership of which he is a member shall be prima facie evidence that such partner is authorized to sign such return, statement, or other document.
(c) Certain partnership elections -