65 ILCS 5/8-10-10
The award of any contract involving amounts in excess of $10,000 shall be made by the purchasing agent to the lowest or highest responsible bidder as provided in Section 8-10-3. Every contract involving amounts in excess of $10,000 shall be signed by the mayor or his duly designated agent, by the comptroller and by the purchasing agent, respectively, of such municipality. Each bid, with the name of the bidder, shall be entered on a record which record with the name of the successful bidder indicated thereon, shall, after award of contract, be open to public inspection in the office of the purchasing agent of such municipality.
All purchase orders or contracts involving amounts of $10,000 or less shall be awarded by the purchasing agent to the lowest or highest responsible bidder as provided in Section 8-10-3 and shall be signed by the purchasing agent and by the comptroller.
An official copy of each awarded purchase order or contract together with all necessary attachments thereto, including assignments and written consents thereto of the purchasing agent as authorized by Section 8-10-14, shall be retained by the purchasing agent in an appropriate file open to the public for such period of time after termination of contract during which action against the municipality might ensue under applicable laws of limitation. After such period such purchase orders, contracts and attachments may be destroyed by direction of the purchasing agent.
65 ILCS 5/8-10-10