Ala. Code § 11-48-48
The municipality, in ordering any local improvement the cost of which or any part thereof is to be assessed against any property in accordance with the provisions of this article, may provide that the same shall be paid in cash within 30 days after the final assessment, provided the cost of such improvement does not exceed $1,000.00, but if the total cost of said improvement is greater than such sum, any property owner may, at his election, to be expressed by notifying the municipal official charged with the duty of collecting such assessments in writing within 30 days after the assessment is made final, pay the said assessment in 10 equal installments, which shall bear interest at a rate not exceeding 12 percent per annum, payable annually; provided, however, that if, on or before the date such assessment is made final, bonds shall have been issued, under the provisions of Division 1 of Article 4 of Chapter 81 of this title, by the municipality for the purpose of providing funds to pay any portion of the costs of such improvement, the rate of interest on such installments may, at the option of the municipality and notwithstanding the foregoing provisions of this paragraph, be fixed by the municipality at a rate not exceeding the "effective net interest rate" on such bonds, as that term is herein defined; and provided, that if the assessment against any lot or parcel of land does not exceed $25.00, said assessment must be paid in cash within 30 days after assessment is made final as above provided.
Any person may pay the whole assessment against any lot or parcel of land within 30 days from the time the assessment is made and may at any installment period pay the assessment in full by paying the full amount of the installments, together with all accrued interest thereon. Should the property owner desire to pay off the deferred installments between the dates on which they are due, he shall pay interest on the same until the succeeding installment period. The first installment shall be payable within 30 days after the assessment is made final, and all assessments or installments thereof shall be payable at the office of the clerk, tax collector, or treasurer of the city or town as may be prescribed, and all assessments or installments thereof shall bear interest at a rate not exceeding 12 percent per annum after the expiration of 30 days from the date on which the same is made final, which interest shall be due and payable at the time and place the assessment or installment is due and payable; provided, however, that if, on or before the date such assessment is made final, bonds shall have been issued, under the provisions of Division 1 of Article 4 of Chapter 81 of this title, by the municipality for the purpose of providing funds to pay any portion of the costs of such improvement, the rate of interest on such assessments or installments may, at the option of the municipality and notwithstanding the foregoing provisions of this paragraph, be fixed by the municipality at a rate not exceeding the "effective net interest rate" on such bonds, as that term is herein defined.
In all cases where the property owner does not elect to pay installments or, having elected to pay in installments, fails to pay the first installment in 30 days from the date of assessment, he shall be held to have waived the right to pay in installments, and the entire assessment shall at the expiration of said 30 days become due and payable.
The term "effective net interest rate" as used in this section means, with respect to any bonds issued as aforesaid for the purpose of providing funds to pay any portion of the costs of improvements, that rate computed by (1) determining, at the rate or rates of interest borne or to be borne by such bonds, the total dollar amount of the interest on such bonds from their date to their respective maturities (and deducting from such amount any premium thereon in excess of face value, or adding to such amount any discount thereon below face value, as the case may be), and (2) dividing such total dollar amount of interest by the sum of the bond year dollars of such bonds - the bond year dollars of each maturity of such bonds to be computed by multiplying the face amount of the bonds maturing in each year by the number of years the bonds of that maturity are outstanding.
Ala. Code § 11-48-48 (1975)