Ga. Code § 48-8-109.2
In any county where a homestead option sales and use tax under Part 1 of this article and a sales tax for purposes of a metropolitan area system of public transportation, as authorized by the amendment to the Constitution set out at Georgia Laws, 1964, page 1008; the continuation of such amendment under Article XI, Section I, Paragraph IV(d) of the Constitution; and the laws enacted pursuant to such constitutional amendment, are being levied, the county governing authority may choose to submit to the electors of the special district the question of whether to suspend the sales and use tax authorized by Code Section 48-8-102 and replace such tax with a sales and use tax authorized by this part. Such referendum shall only be held in conjunction with a referendum submitting to the electors of the special district the question of whether to approve a special purpose local option sales and use tax pursuant to the provisions of Part 1 of Article 3 of this chapter. The electors of the special district must approve both of the sales and use taxes in order for either of them to be implemented. If either of the sales and use taxes is not approved by the electors, the homestead option sales and use tax under Part 1 of this article shall be continued in full force and effect.
OCGA § 48-8-109.2