The IRS determined that Treas. Reg. Sec. 301.6231(a)(1)-1 means that any corporation, including those created under state law, that is not an S corporation is deemed to be a C corporation solely for the purpose of applying the small partnership exception to TEFRA. The TEFRA exception applies to a partnership with 10 or fewer partners, all of whom are individuals or C corporations, absent an affirmative election to be subject to TEFRA. C.C.A. 201530019 (Jun. 17, 2015).