A.R.S. § 48-3760

The district may make any covenant, order any rebate, file any tax return, report any information and order the limitation on the yield of any investment made with the proceeds from the sale of its bonds or with taxes, revenues or other income pledged, held in trust or otherwise used to pay principal, interest and premium, if any, on its bonds in consideration for retaining the exclusion from gross income for federal income tax purposes of the interest income on any bond.