Tenn. Code Ann. § 6-56-305

All purchases, leases, or lease-purchase arrangements with expenditures of less than two thousand five hundred dollars ($2,500) but more than one thousand dollars ($1,000) in any fiscal year may be made in the open market without public advertisement, but shall, whenever possible, be based upon at least three (3) competitive bids. Purchases, leases, or lease-purchases of one thousand dollars ($1,000) or less in any fiscal year shall not require any public advertisement or competitive bidding. Any municipal governing body may, by ordinance, increase the one-thousand-dollar limit in this section to a maximum of forty percent (40%) of the amount established as authorized under § 6-56-306 for purchases requiring public advertisement and competitive bidding.