26 C.F.R. § 1.547-4
The deficiency dividends deduction shall be allowed as of the date the claim is filed. No duplication of deductions with respect to any deficiency dividends is permitted. If a corporation claims and receives the benefit of the provisions of section 547 (or the corresponding section 506 of the Internal Revenue Code of 1939, or section 407 of the Revenue Act of 1938 (52 Stat. 447)), based upon a distribution of deficiency dividends, that distribution does not become a part of the dividends paid deduction under section 561. Likewise, it will not be made the basis of a dividends paid deduction under section 561 by reason of the application of section 563(b), relating to dividends paid after the close of the taxable year and on or before the 15th day of the third month following the close of such taxable year.
26 C.F.R. §1.547-4