Tenn. Code Ann. § 47-14-109: When interest accrues

(a) Interest on negotiable and nonnegotiable instruments shall accrue according to the terms of the instrument; otherwise, interest on the instrument shall accrue as provided in § 47-3-112 .

(b) Liquidated and settled accounts, signed by the debtor, shall bear interest from the time they become due, unless it is expressed that interest is not to accrue until a specific time therein mentioned.

(c) In all other cases, the time from which interest is to be computed shall be the day when the debt is payable, unless another day be fixed in the contract itself.