26 CFR § 53.4943-9 - Business holdings; certain periods.
(a) Taxable period -
(1) In general. For purposes of section 4943, the term “taxable period” means, with respect to any excess business holdings of a private foundation in a business enterprise, the period beginning with the first day on which there are such excess business holdings and ending on the earliest of:
(i) The date of mailing of a notice of deficiency under section 6212 with respect to the tax imposed on the holdings by the section 4943(a);
(ii) The date on which the excess is eliminated; or
(iii) The date on which the tax imposed by section 4943(a) is assessed.
(2) Special rule. Where a notice of deficiency referred to in subparagraph (1)(i) of this paragraph is not mailed because there is a waiver of the restrictions on assessment and collection of a deficiency, or because the deficiency is paid, the date of filing of the waiver or the date of such payment, respectively, shall be treated as the end of the taxable period.
(3) Suspension of taxable period for 90 days. In any case in which a private foundation has excess business holdings solely because of the acquisition of an interest in a business enterprise to which paragraph (a)(1) (ii) or (iii) of § 53.4943-2 applies, the taxable period described in paragraph (a) of this section shall be suspended for the 90-day period (as extended) starting with the date on which the foundation knows or has reason to know of the acquisition, provided that at the end of such period the foundation has disposed of such excess holdings.
(c) Correction. For purposes of section 4943, correction shall be considered as made when no interest in the enterprise held by the foundation is classified as an excess business holdings under section 4943(c)(1). In any case where the private foundation has excess business holdings which are constructively held for it under section 4943(c)(1), correction shall be considered made when either a corporation, partnership, estate, or trust in which holdings in such enterprise are constructively held for the foundation or a disqualified person; the foundation itself; or a disqualified person disposes of a sufficient interest in the enterprise so that no interest in the enterprise held by the foundation is classified as excess business holdings under section 4943(c)(1).