70 ILCS 2605/9bb
In addition to the corporate working cash fund bonds authorized by Section 9b of this Act, the corporate authorities of any such sanitary district, to provide money for the corporate working cash fund, may levy annually upon all taxable property within the territorial limits of such sanitary district, commencing with the budget year 1972, a tax at a rate not to exceed .005% of the value of all taxable property within such sanitary district as equalized or assessed by the Department of Revenue. The aggregate amount which may be accumulated in such working cash fund from the proceeds of bonds issued, the tax levy and amounts transferred from the construction working cash fund, shall never exceed 90% of the amount produced by multiplying the maximum corporate tax rate permitted under this Act by the last known equalized assessed valuation of all property within the territorial boundaries of the sanitary district at the time any bonds are issued or taxes are levied. The collection of any such tax shall not be anticipated by the issuance of any warrants or notes drawn against the same. Such tax shall be levied and collected in like manner with all other taxes of such sanitary district. It shall be known as the corporate working cash fund tax and shall be in addition to the maximum of all other taxes and tax rates which such sanitary district is now, or may hereafter be, authorized by law to levy upon the aggregate valuation of all taxable property within such sanitary district.
70 ILCS 2605/9bb