26 CFR § 1.269-1 - Meaning and use of terms.
As used in section 269 and §§ 1.269-2 through 1.269-7:
(a) Allowance. The term allowance refers to anything in the internal revenue laws which has the effect of diminishing tax liability. The term includes, among other things, a deduction, a credit, an adjustment, an exemption, or an exclusion.
(c) Control. The term control means the ownership of stock possessing at least 50 percent of the total combined voting power of all classes of stock entitled to vote, or at least 50 percent of the total value of shares of all classes of stock of the corporation. For control to be “acquired on or after October 8, 1940”, it is not necessary that all of such stock be acquired on or after October 8, 1940. Thus, if A, on October 7, 1940, and at all times thereafter, owns 40 percent of the stock of X Corporation and acquires on October 8, 1940, an additional 10 percent of such stock, an acquisition within the meaning of such phrase is made by A on October 8, 1940. Similarly, if B, on October 7, 1940, owns certain assets and transfers on October 8, 1940, such assets to a newly organized Y Corporation in exchange for all the stock of Y Corporation, an acquisition within the meaning of such phrase is made by B on October 8, 1940. If, under the facts stated in the preceding sentence, B is a corporation, all of whose stock is owned by Z Corporation, then an acquisition within the meaning of such phrase is also made by Z Corporation on October 8, 1940, as well as by the shareholders of Z Corporation taken as a group on such date, and by any of such shareholders if such shareholders as a group own 50 percent of the stock of Z on such date.