65 ILCS 5/8-4.1-6

The corporate authorities are authorized and may covenant and contract with the holders of Revenue Bonds to levy, charge and collect moneys pledged as security for the payment of Revenue Bonds in amounts sufficient to provide for the prompt payment of the principal of and interest on such Bonds, and to provide an additional amount of money, as debt service coverage, computed as a percentage of the amount of principal and interest scheduled to be payable in any given year.