taxable period
(5) Taxable period The term “taxable period” means, with respect to any excess benefit transaction, the period beginning with the date on which the transaction occurs and ending on the earliest of— (A) the date of mailing a notice of deficiency under section 6212 with respect to the tax imposed by subsection (a)(1), or (B) the date on which the tax imposed by subsection (a)(1) is assessed.