(a) For purposes of this article, the term "post-termination transition period" means:
(1) The period beginning on the day after the last day of the corporation's last taxable year as an Alabama S corporation and ending on the later of:
a. The day which is one year after the last day.
b. The due date for filing the return for the last year as an Alabama S corporation, including extensions.
(2) The 120-day period beginning on the date of a determination pursuant to an audit of the taxpayer which follows the termination of the corporation's election to be treated as a federal S corporation and which adjusts a subchapter S item of income, loss, or deduction of the corporation arising during the S period.
(3) The 120-day period beginning on the date of a determination that the corporation's election under 26 U.S.C. § 1362 had terminated for a previous taxable year.
(b) For purposes of subsection (a), the term "determination" means:
(1) A determination as defined in 26 U.S.C. § 1313(a); or
(2) An agreement between the corporation and the U.S. Secretary of the Treasury that the corporation failed to qualify as an S corporation.