When any special assessment is made under this Act, the ordinance authorizing such assessment may provide that the entire assessment and each individual assessment be divided into annual installments, not more than twenty in number. In all cases such division shall be made so that all installments shall be equal in amount, except that all fractional amounts shall be added to the first installment so as to leave the remaining installments of the aggregate equal in amount and each a multiple of $100. The said several installments shall bear interest at a rate not to exceed that permitted for public corporation bonds under “An Act to authorize public corporations to issue bonds, other evidences of indebtedness and tax anticipation warrants subject to interest rate limitations set forth therein”, approved May 26, 1970, as now or hereafter amended, except that for the purposes of this Section, “the time the contract is made” shall mean the date of adoption of the original ordinance authorizing the assessment; both principal and interest shall be payable, collected and enforced as they shall become due in the manner provided for the levy, payment, collection and enforcement of such assessments and interest, as provided in Divisions 1 and 2 of Article 9 and Division 87 of Article 11 of the “Illinois Municipal Code”, approved May 29, 1961, as heretofore or hereafter amended.