(1) In the event that a person required to pay estimated taxes under section 63-3036A, Idaho Code, fails to pay such estimated taxes or fails to pay the full amount of estimated taxes due, the state tax commission shall assess interest on such unpaid or underpaid estimated taxes at the rate of interest set in section 63-3045, Idaho Code, as the interest to be assessed on a deficiency in taxes.
(2) Interest shall be computed on the difference between the amount of estimated payment required to be made on each quarterly report and the amount of quarterly payment actually made. Interest shall apply from the due date of the quarterly report until the required amount is paid, or until, excluding extensions, the due date of the return, whichever is first.