IRC § 1361(b)(3)
F Reorganization Upon S Corp Merger Into Its QSub
When an S corporation merges into its own qualified subchapter S subsidiary under state law, the QSub election terminates and the surviving subsidiary can qualify as an F reorganization.
Treas. Reg. § 1.1361-5(b)(3), Example 8 • Qualified Subchapter S Subsidiaries