105 ILCS 5/17-16
When there is no money in the treasury of any school district having a population of 500,000 or less inhabitants, whether governed by either or both the general school laws or any special charter, to defray the necessary expenses of the district, including amounts necessary to pay maturing principal and interest of bonds, the school board may issue warrants, or may provide a fund to meet the expenses by issuing and disposing of warrants, drawn against and in anticipation of any taxes levied for the payment of the necessary expenses of the district, either for transportation, educational or for all operations and maintenance purposes, or for payments to the Illinois Municipal Retirement Fund, or for the payment of maturing principal and interest of bonds, or for fire prevention, safety, energy conservation and school security purposes, as the case may be, to the extent of 85% of the total amount of the tax so levied. The warrants shall show upon their face that they are payable in the numerical order of their issuance solely from such taxes when collected, and shall be received by any collector of taxes in payment of the taxes against which they are issued, and such taxes shall be set apart and held for their payment.
Every warrant shall bear interest, payable only out of the taxes against which it is drawn, at a rate not exceeding the maximum rate authorized by the Bond Authorization Act, as amended at the time of the making of the contract, if issued before July 1, 1971 and if issued thereafter at the rate of not to exceed the maximum rate authorized by the Bond Authorization Act, as amended at the time of the making of the contract, from the date of its issuance until paid or until notice shall be given by publication in a newspaper or otherwise that the money for its payment is available and that it will be paid on presentation, unless a lower rate of interest is specified therein, in which case the interest shall be computed and paid at the lower rate.
With respect to instruments for the payment of money issued under this Section either before, on, or after the effective date of this amendatory Act of 1989, it is and always has been the intention of the General Assembly (i) that the Omnibus Bond Acts are and always have been supplementary grants of power to issue instruments in accordance with the Omnibus Bond Acts, regardless of any provision of this Act that may appear to be or to have been more restrictive than those Acts, (ii) that the provisions of this Section are not a limitation on the supplementary authority granted by the Omnibus Bond Acts, and (iii) that instruments issued under this Section within the supplementary authority granted by the Omnibus Bond Acts are not invalid because of any provision of this Act that may appear to be or to have been more restrictive than those Acts.
105 ILCS 5/17-16