O.C.G.A. § 48-5-48.7 (2019)

(a) Any document required to be filed under Code Section 48-5-48.1 or 48-5-48.5 shall be considered properly and timely filed if the postal date on the mailed document, whether metered or stamped, is on or before the date on which the tax receiver or tax commissioner of the county in which the property is located closes the book for the return of taxes.

(b) Any document properly and timely filed pursuant to subsection (a) of this Code section and incorrectly determined to be untimely filed, upon sufficient proof thereof, shall entitle the applicant to a credit against future ad valorem assessments from the county which improperly denied the applicant the exemption under Code Section 48-5-48.1 or 48-5-48.5.