65 ILCS 5/8-4-13
Every municipality incorporated by and operating under a special charter may borrow money upon the credit of the municipality for lawful corporate purposes, including the funding and refunding of any judgment indebtedness heretofore or hereafter incurred, and may issue its negotiable coupon bonds therefor in such form, of such denomination, payable at such place and at such time or times, not exceeding 20 years from their date, as the corporate authorities of the municipality may prescribe by ordinance.
Every such municipality, prior to or at the time of issuing its bonds under this section, shall provide for the collection of a direct annual tax upon all of the taxable property of the municipality, which, in addition to all other taxes, shall be sufficient to pay the interest on the bonds as it falls due and also to pay the principal of the bonds within 20 years from their date.
65 ILCS 5/8-4-13