65 ILCS 5/8-1-11
Whenever a municipality does not have sufficient money in its treasury to meet all necessary expenses and liabilities of the municipality, including all expenses for building purposes, the corporate authorities may issue and sell warrants drawn against and in anticipation of taxes already levied for the particular funds from which these expenses and liabilities may be paid, to the extent of 85% of the total amount of those taxes. However, in municipalities in which there has been created a working cash fund pursuant to the provisions of Division 6 of this Article 8, no tax anticipation warrants shall be drawn against taxes levied for general corporate purposes for such an amount that the aggregate of (1) the amount of those warrants, and the interest to accrue thereon, and (2) the aggregate amount of those warrants theretofore drawn against those taxes and the interest accrued and to accrue thereon, and (3) the aggregate amount of money theretofore transferred from the working cash fund to the general fund of that municipality, exceeds 90% of the actual or estimated amount of those taxes extended or to be extended by the county clerk upon the books of the collector or collectors of state and county taxes within that municipality. Tax anticipation warrants drawn and issued under this section shall show upon their face that they are payable in the numerical order of their issuance solely from the anticipated taxes when these anticipated taxes are collected and not otherwise. These warrants shall be received by any collector of taxes in payment of the taxes against which they are issued, and the taxes against which these warrants are drawn shall be set apart and held for their payment.
65 ILCS 5/8-1-11