Tennessee Code Title 67. Taxes and Licenses § 67-1-107

(1) Transmitted through the United States mail or any alternative delivery service as authorized by § 7502 of the Internal Revenue Code (26 U.S.C. § 7502), shall be deemed filed and received by the state or political subdivision on the date shown by the post office cancellation mark stamped on the envelope or other appropriate wrapper containing it;

(2) Mailed but not received by the state or political subdivision, or where received and the cancellation mark is illegible, erroneous or omitted, shall be deemed filed and received on the date it was mailed, if the sender establishes by competent evidence that the tax report, claim, appeal, return, statement, remittance or other tax document was deposited in the United States mail; provided, that in cases of such nonreceipt of a tax report, claim, appeal, return, statement, remittance or other tax document required by law to be filed, the sender files with the state or political subdivision a duplicate thereof within ten (10) days after written notification is given to the sender by the state or political subdivision of the nonreceipt of such tax report, claim, appeal, return, statement, remittance, or other tax document; or

(3) Transmitted as provided in subdivision (a)(1) to the state or political subdivision and postmarked or delivered no more than twenty-four (24) hours subsequent to the last date for the timely filing of such document or payment, shall not be considered delinquent and shall preserve any rights otherwise dependent on timely filing; however, any such document or payment, transmitted as provided in subdivision (a)(1) to the state or political subdivision and postmarked or delivered more than twenty-four (24) hours subsequent to the last date for timely filing, shall be subject to any late charges, penalty or interest otherwise chargeable without regard to the twenty-four-hour grace period as provided in this subdivision (a)(3).