Under Georgia law, a taxpayer has two remedies to challenge its tax assessment: (1) an appeal under O.C.G.A. § 48-5-311 and (2) a refund demand under O.C.G.A. § 48-5-380. An appeal under O.C.G.A. § 48-5-311 is the most efficient way to challenge your tax assessment; however, it is subject to strict time deadlines, e.g., 45 days after the notice of assessment. For later discovered errors or illegally assessed or collected taxes, a taxpayer has up to five years to file a refund demand under O.C.G.A. § 48-5-380. While not an exhaustive list, the Court in Nat'l Health Network, Inc. v. Fulton County, confirmed that a claim for a tax refund would be proper in the following situations:

1. a taxing authority assessed and collected taxes in violation of federal or state law;
2. a taxpayer asserts that the property assessed was exempt from taxation
3. a county or city applied the wrong millage rate to the assessed value;
4. a taxpayer made duplicate payments or paid taxes to the wrong taxing authority; 
5. a county or city collected property taxes for land that was located in another county or owned by a different person; or
6. the county committed a clerical error, such as listing the wrong assessed value.

Nat'l Health Network, Inc. v. Fulton County, 270 Ga. 724, 727-728 (1999)(citations omitted).