O.C.G.A. § 34-8-178 (2019)

Any employer may make voluntary payments in addition to the contributions required under this chapter, and the same shall be credited to the employer’s experience account; provided, however, that such voluntary contributions shall not be used in the computation of reduced rates unless such contributions are paid within 30 days following the date upon which the Commissioner mails notice that such payments may be made with respect to a calendar year, and in no event shall such payments be made later than the expiration of 120 days after the beginning of the year for which such rates are effective. Such voluntary payments when accepted from an employer will not be refunded in whole or in part.