710:50-13-8 Interest on underpayment of estimated tax; exceptions

(a) Interest is levied at 20% per annum, for the period of underpayment, on any underpayment of the "required annual payment" of estimated tax, as that term is defined by 68 O.S. § 2385.9(B) and 710:50-13-7. (b) The amount of the underpayment equals the excess of the required installment over the amount paid on or before the due date of the installment. The period of underpayment runs from the due date of the required installment to the earlier of the fifteenth day of the fourth month, or for corporations, thirty days after the due date for returns established under the Internal Revenue Code, following the close of the taxable year or the date on which the required installment is paid. (c) Provided, however, no interest will be added to the tax if: (1) The tax shown on the return for the taxable year is less than One Thousand Dollars ($1,000.00); or (2) The taxpayer was an Oklahoma resident throughout the preceding taxable year of twelve (12) months and did not have any liability for tax for the preceding taxable year. (d) OTC Form OW-8-P is a schedule provided for calculating interest for underestimating and also provides for an exception for fluctuations of income throughout the year.