Tennessee Code Title 6. Cities and Towns § 6-22-128

No contract, agreement, or other obligation involving the expenditure of money shall be entered into, nor shall any ordinance, resolution or order for the expenditure of money be passed by the board of commissioners or be authorized by any officer of the city, unless the finance director shall first certify to the board or the proper officer, as the case may be, that the money required for such contract, agreement, obligation or expenditure, is in the treasury or safely assured to be forthcoming and available in time to comply with, or meet such contract, agreement, obligation or expenditures; and no contract, agreement or other obligation involving the expenditure of money payable from the proceeds of bonds of the city shall be entered into until the issuance and sale of such bonds have been duly authorized in accordance with the provisions of this charter in reference to city bonds.