26 CFR 1.507-5 - Aggregate tax benefit; in general.
(1) The aggregate increases in tax under chapters 1, 11, and 12 (or the corresponding provisions of prior law) which would have been imposed with respect to all substantial contributors to the foundation if deductions for all contributions made by such contributors to the foundation after February 28, 1913, had been disallowed,
(2) The aggregate increases in tax under chapter 1 (or the corresponding provisions of prior law) which would have been imposed with respect to the income of the private foundation for taxable years beginning after December 31, 1912, if (i) it had not been exempt from tax under section 501(a) (or the corresponding provisions of prior law), and (ii) in the case of a trust, deductions under section 642(c) (or the corresponding provisions of prior law) had been limited to 20 percent of the taxable income of the trust (computed without the benefit of section 642(c) but with the benefit of section 170(b)(1)(A)),
(4) Interest on the increases in tax determined under subparagraphs (1), (2), and (3) of this paragraph from the first date on which each such increase would have been due and payable to the date on which the organization ceases to be a private foundation.
(b)Contributions. In computing the amount of the aggregate increases in tax under subparagraph (1) of this paragraph, all deductions attributable to a particular contribution shall be included. For example, if a substantial contributor has taken deductions under sections 170 and 2522 (or the corresponding provisions of prior law) with respect to the same contribution, the amount of each deduction shall be included in the computations under section 507(d)(1)(A). Accordingly, the aggregate tax benefit may exceed the fair market value of the property transferred.