Tenn. Code Ann. § 9-23-104

Notwithstanding any tax increment statute or any plan to the contrary, no allocation of tax increment revenues shall be made with respect to any property for a period of more than twenty (20) years in the case of an economic impact plan, or thirty (30) years in the case of a redevelopment plan or community redevelopment plan as defined in § 9-23-102, unless both the commissioner and the comptroller have made a written determination that a longer period is in the best interest of the state. If the written determination approving or declining the longer term is not rendered within thirty (30) days, the longer term is deemed approved.