See https://s3.amazonaws.com/emma-assets/40ecb/1f4578ef86728c0e49ebb61cd22d6100/Withholding_Requirements...
Which says, in pertinent parts
The rate of withholding is 3 percent of the sales price. An
alternative for calculating the withholding is to use the seller’s gain. In
order to apply the withholding to the gain, the seller must complete form
ITAFF2 (Affidavit of Seller’s Gain) attesting to the amount of the taxable gain.
The buyer or transferee is required to provide the seller
with a copy of the G- 2RP or other form for the seller to file with the
seller’s income tax return. (This form documents the withholding)
https://dor.georgia.gov/sites/dor.georgia.gov/files/related_files/document/TSD/Form/TSD_Withholding_...
