710:50-13-7 "Required annual payment" of estimated tax defined

(a) "Required annual payment", as used in this Section, means the lesser of: (1) Seventy percent (70%) of the tax shown on the return for the taxable year; or (2) One Hundred percent (100%) of the tax shown on the return for the preceding taxable year of twelve (12) months. (b) Where income has not been earned evenly throughout the year, the required annual payment of estimated tax may also be computed pursuant to the provisions of 710:50-13-9, 68 O.S. § 2385.9(C), and applicable sections of the Internal Revenue Code. (c) Interest is levied at 20% per annum, computed per quarter, on any underpayment of the required annual payment of estimated tax.