Taxpayers subject to the requirements of estimated tax payments for an income year ending after December 31, 1983, shall estimate an amount not less than eighty percent (80%) of the tax actually due in the case of an individual or, except as otherwise provided in Section 27-7-329(f), an amount not less than ninety percent (90%) of the tax actually due in the case of a corporation. Any corporate taxpayer which either fails to file the required estimated tax returns and pay the tax within the time prescribed, or, except as otherwise provided in Section 27-7-329(f), which underestimates the required amount of the estimated tax shall be liable for a penalty in the amount of ten percent (10%) of the amount unpaid plus interest at the rate of one percent (1%) per month on such amount, except as otherwise provided in this section. Any individual taxpayer who either fails to file the required estimated tax returns and pay the tax within the time prescribed, or who underestimates the required amount of the estimated tax shall be liable for interest at the rate of one percent (1%) per month on such amount, except as otherwise provided in this section. For taxes assessed by the commissioner on or after January 1, 2015, the rate of any interest assessed under this section shall be:
Nine-tenths of one percent (9/10 of 1%) per month for such taxes assessed on or after January 1, 2015, and before January 1, 2016;
Eight-tenths of one percent (8/10 of 1%) per month for such taxes assessed on or after January 1, 2016, and before January 1, 2017;
Seven-tenths of one percent (7/10 of 1%) per month for such taxes assessed on or after January 1, 2017, and before January 1, 2018;
Six-tenths of one percent (6/10 of 1%) per month for such taxes assessed on or after January 1, 2018, and before January 1, 2019; and
One-half of one percent (1/2 of 1%) per month for such taxes assessed on or after January 1, 2019.