65 ILCS 5/8-10-7
All proposals to award purchase orders or contracts involving amounts in excess of $10,000 shall be published at least 10 days, excluding Sundays and legal holidays, in advance of the date announced for the receiving of bids, in a secular English language daily newspaper of general circulation throughout such municipality and shall simultaneously be posted on readily accessible bulletin boards in the office of the purchasing agent. Nothing contained in this section shall be construed to prohibit the purchasing agent from placing additional announcements in recognized trade journals. Advertisements for bids shall describe the character of the proposed contract or agreement in sufficient detail to enable the bidders thereon to know what their obligations will be, either in the advertisement itself, or by reference to detailed plans and specifications on file at the time of the publication of the first announcement. Such advertisement shall also state the date, time and place assigned for the opening of bids, and no bids shall be received at any time subsequent to the time indicated in the announcement. However, an extension of time may be granted for the opening of such bids upon publication in a secular English newspaper of general circulation throughout such municipality of the date to which the bid opening has been extended. The time of the bid extension opening shall not be less than 5 days after the publication thereof, Sundays and legal holidays excluded.
Cash, cashier's check, a certified check, a comptroller's certificate of moneys owed the particular vendor, or a bid bond with adequate surety approved by the purchasing agent as a deposit of good faith, in a reasonable amount, but not in excess of 10% of the contract amount may be required of each bidder by the purchasing agent on all bids involving amounts in excess of $10,000 and, if so required, the advertisement for bids shall so specify.
65 ILCS 5/8-10-7