"Retailer" and "seller" include every person:
The department, when necessary for the efficient administration of this chapter, may treat any salesman, representative, trucker, peddler, or canvasser as the agent of the dealer, distributor, supervisor, employer, or other person under whom they operate or from whom they obtain the tangible personal property sold by them, regardless of whether they are making sales on their own behalf or on behalf of the dealer, distributor, supervisor, employer, or other person. The department may also treat the dealer, distributor, supervisor, employer, or other person as a retailer for purposes of this chapter.
S.C. Code § 12-36-70
2019 Act No. 21, Section 1, provides as follows:
"SECTION 1. The General Assembly finds:
"(1) the South Carolina Sales and Use Tax Act requires any person engaged in business as a retailer to remit the sales and use tax on all retail sales of tangible personal property not otherwise excluded or exempted from the tax. This requirement applies to all retail sales of tangible personal property by the retailer, whether the tangible personal property is owned by the retailer or another person. Retailers selling tangible personal property at retail on consignment, by auction, or in any other manner must remit the sales and use tax on such retail sales;
"(2) the Internet marketplaces where a person sells tangible personal property at retail by listing or advertising, or allowing the listing or advertising of, another person's products on an online marketplace and collects or processes the payment from the customer are retailers required to remit the sales and use tax on such retail sales under the provisions of South Carolina sales and use tax law;
"(3) with the changing economy and ever expanding role of the Internet in the retail market, the longstanding requirement in the sales and use tax law that a retailer remit the tax on retail sales of tangible personal property owned by another person must apply to all retailers, including both Internet retailers and brick and mortar retailers;
"(4) retailers selling another person's tangible personal property on the Internet must clearly understand and be informed of their requirements to remit the sales and use tax in the same manner as retailers selling another person's tangible personal property in a brick and mortar store; and
"(5) this act shall not be construed as a statement concerning the applicability of the South Carolina Sales and Use Tax Act to any sales and use tax liability in matters currently in litigation or being audited."