Tenn. Code Ann. § 65-7-114

When the subscription so made becomes due, as provided, it is made the duty of the county legislative body, or municipal authorities, as the case may be, on the receipt of the certificates of stock, as provided in § 65-7-116, to levy, from time to time, such taxes upon the taxable property, privileges, and persons liable by law to taxation within the county or corporate limits, as the case may be, as will be sufficient and necessary to meet the maturing interest on the bonds of such county, town, or city, and to provide for the payment of the principal; provided, that no tax to pay such subscription exceeding twenty-five percent (25%) of the amount subscribed shall be levied in any one (1) year.