The financial officer may establish a separate rebate fund to be used to make any payments to the United States with respect to investment earnings on proceeds that may be required by the Internal Revenue Code. There may be separate accounts within the rebate fund. Amounts deposited to the rebate fund shall be used only for the purpose of making rebate payments, and no appropriation will be required before payment of any required rebates from the rebate fund to the United States. The financial officer may make payments from the rebate fund as required in order to: comply with the Internal Revenue Code; and maintain the exclusion from gross income for federal income tax purposes of interest on the bonds. Any excess money held in the rebate fund with respect to an issue of bonds after all required rebate payments for that issue have been made, as certified by the financial officer, shall be applied in a manner consistent with the Internal Revenue Code.