105 ILCS 5/34-23
When there is not sufficient money in the treasury to meet the ordinary and necessary expenses for educational and for building purposes, and for the purpose of paying the principal of and interest on bonds to order issued warrants against and in anticipation of any taxes levied for the payment of the expenditures for educational and for building purposes, and for the purpose of paying the principal of and interest on bonds, to the extent of 85% of the total amount of the taxes levied for such purpose; provided, that whenever a working cash fund has been created pursuant to Sections 34-30 through 34-36 warrants shall at no time be drawn against any such taxes levied for educational purposes for such an amount that the aggregate of (a) the amount of such warrants, with the interest to accrue thereon, (b) the aggregate amount of warrants theretofore drawn against such taxes and the interest accrued and to accrue thereon, and (c) the aggregate amount of money theretofore transferred from the working cash fund to the educational purposes fund exceeds 90% of the actual or estimated amount of such taxes extended or to be extended by the county clerk upon the books of the collector or collectors of State and county taxes within the school districts. Warrants may, however, be issued against and in anticipation of any taxes levied for the expenditures for building purposes to the extent of 90% of the total amount of taxes levied for such purposes whenever and only if the board in connection with a grant of money from the federal government or a pledge to any agency, instrumentality, corporation, administration or bureau of the United States of America in connection with such grant, sells or pledges to the federal government or to any agency, instrumentality, corporation, administration or bureau of the United States of America, warrants issued in excess of 75% but not exceeding 90% of the total amount of taxes levied for the payment of the expenditures for building purposes.
105 ILCS 5/34-23