7-12-4189. Simple interest on assessments. (1) Except as provided in subsection (3), simple interest must be charged on all special assessments and taxes levied and assessed in accordance with any of the provisions of this part. The simple interest must be charged at an annual rate equal to the sum of:

(a) 1/2 of 1% a year; plus

(b) the average interest rate payable on the outstanding bonds or warrants of the special improvement district at the time the assessment is levied each fiscal year; plus

(c) at the option of the city or town council, up to an additional 1/2 of 1% a year.

(2) The city or town council may subsequently reduce or eliminate the additional interest rate allowed under subsection (1)(c). If the additional interest rate is reduced or eliminated, it may not be subsequently increased or reimposed.

(3) If and so long as the bonds or warrants secured by the assessments bear interest at a variable rate, the installments of assessments remaining unpaid must bear simple interest at an annual rate equal to the sum of:

(a) 1% a year; plus

(b) the interest rate payable on the outstanding bonds or warrants of the rural special improvement district at the time the assessment is levied each fiscal year; plus

(c) to the extent that the interest rate on the bonds or warrants is then less than the maximum rate prescribed for the bonds or warrants or if there is no prescribed maximum rate, up to an additional 1% a year, as may be prescribed by the board of county commissioners in the resolution authorizing the issuance or sale of the bonds or warrants.

(4) The treasurer, in collecting the special assessment taxes if the taxes are payable in one installment, shall collect the interest shown to be due on the taxes by the resolution levying the assessment. If the assessment is payable in installments, the treasurer shall, at the time of collecting the first installment, collect the interest shown to be due on the assessment by the resolution levying the assessment, and the treasurer shall collect with each subsequent installment interest on the amount remaining unpaid.