26 CFR § 1.642(c)-4 - Nonexempt private foundations.
In the case of a trust which is, or is treated under section 4947(a)(1) as though it were, a private foundation (as defined in section 509(a) and the regulations thereunder) that is not exempt from taxation under section 501(a) for the taxable year, a deduction for amounts paid or permanently set aside, or used for a purpose specified in section 642(c) (1), or (2) shall not be allowed under § 1.642(c)–1 or § 1.642(c)–2, but such trust shall, subject to the provisions applicable to individuals, be allowed a deduction under section 170 for charitable contributions paid during the taxable year. Section 642(c)(6) and this section do not apply to a trust described in section 4947(a)(1) unless such trust fails to meet the requirements of section 508(e). However, if on October 9, 1969, or at any time thereafter, a trust is recognized as being exempt from taxation under section 501(a) as an organization described in section 501(c)(3), if at such time such trust is a private foundation, and if at any time thereafter such trust is determined not to be exempt from taxation under section 501(a) as an organization described in section 501(c)(3), section 642(c)(6) and this section will apply to such trust. See § 1.509 (b)–1 (b).