The county board of any such county shall have the power to levy annually a tax to provide moneys for such working cash fund at a rate not to exceed .02% of value, as equalized or assessed by the Department of Revenue. The aggregate amount in such working cash fund shall never exceed $20,000,000. The collection of any such tax shall not be anticipated by the issuance of any warrants drawn against the same. Such tax shall be levied and collected, except as herein otherwise provided, in like manner with the general taxes of such county. It shall be known as the working cash fund tax, and shall be in addition to the maximum of all other taxes and tax rates which such county is now, or may hereafter be, authorized by law to levy upon the aggregate valuation of all taxable property within such county. The tax may be levied by separate resolution on or before the 3rd Tuesday in September in each year, for the purpose herein authorized, without any appropriation thereof being made in the resolution termed the annual appropriations bill, or otherwise.