The first installment under Plan One or Plan Two shall include interest from the date of approval of the assessment roll with the finance officer of the municipality to May first of the year in which the first installment is due. Each subsequent installment shall include one year's interest. Each of the installments, including interest as provided above, becomes delinquent on May first of the year in which the installment becomes due and shall have interest and penalty added each month at the same rate as provided in § 10-21-23 for delinquent real estate taxes.
SDCL 9-43-109