605 ILCS 5/10-206
If the cost of such construction or repair is $1,000 or less, such county (or counties) shall not be liable for any part of such expense until all the work has been fully completed, and has been accepted by the county superintendent of highways (or by each county superintendent of highways). Such official (or officials) shall certify such acceptance to his county board (or to their respective county boards), and shall accompany such certificate with an itemized statement of all expenditures in such construction or repair.
If the total cost of the construction or repair exceeds $1,000, partial payments not oftener than once a month, and not to exceed 90% of the work actually completed, may be paid the contractor by the county (or counties). No such partial payments shall be made unless approved by the county superintendent of highways (or by each county superintendent of highways), and no partial payments shall in any way be deemed an acceptance of the work until such work has been fully completed and accepted by the county superintendent (or by each county superintendent of highways) and such acceptance certified as provided above.
605 ILCS 5/10-206