Tenn. Code Ann. § 12-4-704: Interest

(a) Interest shall accrue and be charged on payments overdue under § 12-4-703 at one and one-half percent (1½%) per month beginning on the day after payment is due.

(b) Interest which is unpaid at the end of each sixty-day period or at the end of any specified period provided by contract shall be added to the principal amount of the debt and shall thereafter accumulate interest.