(1) Interest accrues on unpaid or delinquent taxes as provided in 15-1-216. The interest must be computed from the date on which the statement and tax were originally due.
(2) If the payment of a tax deficiency is not made within 60 days after it is due and payable and if the deficiency is due to negligence on the part of the taxpayer but without fraud, the penalty imposed by 15-1-216 (2) must be added to the amount of the deficiency.