taxable period
(2) Taxable period The term “taxable period” means, with respect to any excess business holdings of a private foundation in a business enterprise, the period beginning on the first day on which there are excess holdings and ending on the earlier of— (A) the date of mailing of a notice of deficiency with respect to the tax imposed by subsection (a) under section 6212 in respect of such holdings, or (B) the date on which the tax imposed by subsection (a) in respect of such holdings is assessed.