605 ILCS 5/5-409
Partial payments on contracts let by a county for highway work may be made as the work progresses but no payment in excess of 90% of the value of the work then completed may be made until 50% of the work has been completed. After 50% of the work is completed, the county may, in its discretion, make partial payments without any further retention, provided that satisfactory progress is being made and provided that the amount retained is not less than 5% of the total adjusted contract price.
At the discretion of the county and with the consent of the surety, a semi-final payment may be made when the principal items of the work have been satisfactorily completed. Such payment shall not exceed 90% of the amount retained nor reduce the amount retained to less than 1% of the adjusted contract price nor less than $500.00.
Final payment under the contract shall not be made until it is shown that all money due for any labor, material, apparatus, fixtures or machinery furnished to the contractor or other indebtedness of the contractor incurred in connection with such work has been paid.
Furthermore, if the contract is one that was approved by the Department, no final payment shall be made until the county has received approval by the Department to do so.
This Section is also subject to the provisions of Section 23 of the Mechanics Lien Act .
605 ILCS 5/5-409