65 ILCS 5/9-2-49
Whenever an ordinance provides for the making of a local improvement which comprises either the construction of an improvement or the taking or damaging of property therefor, or both such construction and taking or damaging, and proceedings are instituted prior to, on or after January 1, 1942, for the confirmation of a special assessment or a special tax to defray the whole or any portion of the cost of any such improvement, including the cost of the construction thereof and the compensation for the taking or damaging of property therefor, or including only the cost of taking or damaging of property therefor, and including in each such proceeding the cost of making and collecting the special assessment or special tax (in the case of such municipalities as may lawfully include that cost in special assessment or special tax proceedings), the corporate authorities may provide by the ordinance for any such local improvement, or if proceedings authorized by any such ordinance have been filed in court, then by an ordinance passed at any time before the confirmation of the assessment roll filed in any such proceeding, that the aggregate amount assessed to defray the cost of the improvement, including the cost of the construction thereof and the compensation for the taking or damaging of property therefor or including only the cost of taking or damaging property therefor, and each individual assessment and also the assessment against the municipality on account of property owned by the municipality and for public benefits, be divided into not more than 20 installments. Such installments shall be equal in amount and each a multiple of $100, except that any fractional amounts of the aggregate assessment, after division as aforesaid, shall be apportioned to the first installment. However, if it is so provided by ordinance passed at any time before the confirmation of the assessment roll, so much of the aggregate amount assessed as represents the cost of the construction of the improvement shall be divided into as many parts as there are installments, which parts shall be equal in amount and each a multiple of $100, except that any fractional amounts of the cost of construction after division as aforesaid shall be apportioned to the first installment, and so much of the aggregate amount assessed as represents the compensation for property to be taken or damaged, together with the cost of making and collecting the special assessment or special tax (in the case of such municipalities as may lawfully include that cost in special assessment or special tax proceedings) shall be apportioned to the first installment of the special assessment or special tax.
65 ILCS 5/9-2-49