IRC § 1361(b)(3)
Stock for Stock Exchange and QSub Election
A corporation acquires all of the stock of a target solely in exchange for its own voting stock, then makes an S election and a QSub election, producing a reorganization described in section 368(a)(1)(C).
Treas. Reg. § 1.1361-4(a)(2)(ii), Example 2 • Qualified Subchapter S Subsidiaries