Tenn. Code § 49-3-1007
If any special school district has bonds outstanding payable from taxes levied by special act of the general assembly, and if at any time the amount on deposit in the special fund created solely for the purpose of paying principal of and interest on the bonds is equal to at least two hundred percent (200%) of the amount of the principal and interest coming due on the bonds in the next twelve (12) months next succeeding, excluding any portion of principal and interest budgeted at the beginning of each fiscal year to be paid from sales tax revenues, TISA funds, or a combination of sales tax revenues or TISA funds, hereinafter referred to as annual debt service requirements, the special district by resolution may, on or before September 1 of any year, certify to the county trustee the special school district tax rate, not to exceed the rate imposed by existing legislative act, necessary to raise the amount of taxes that must be collected in order to maintain the special fund during the succeeding year in an amount equal to at least two hundred percent (200%) of annual debt service requirements, and the county trustee shall collect only the taxes based on the rate so certified.
T.C.A. § 49-3-1007