For "large corporate underpayment" as defined in I.R.C. Sec. 6621, the interest rate on underpayment shall be as prescribed by I.R.C. Sec. 6621(c)(1).
(Section 40-1-44, Code of Alabama 1975 and Internal Revenue Code 26 U.S.C. 6621) (Adopted through APA effective February 16, 1999)