Conn. Gen. Stat. § 12-408e

(1) “Marketplace facilitator” means any person who (A) facilitates retail sales of at least two hundred fifty thousand dollars during the prior twelve-month period by marketplace sellers by providing a forum that lists or advertises tangible personal property subject to tax under this chapter or taxable services, including digital goods, for sale by such marketplace sellers, (B) directly or indirectly through agreements or arrangements with third parties, collects receipts from the customer and remits payments to the marketplace sellers, and (C) receives compensation or other consideration for such services;

(2) “Marketplace seller” means any person who has an agreement with a marketplace facilitator regarding retail sales of such person, whether or not such person is required to obtain a permit under section 12-409 ; and

(3) “Forum” means a physical or electronic place, including, but not limited to, a store, a booth, an Internet web site, a catalog or a dedicated sales software application, where tangible personal property or taxable services are offered for sale.

(b) (1) A marketplace facilitator shall be considered the retailer of each sale such facilitator facilitates on its forum for a marketplace seller. Each marketplace facilitator shall (A) be required to collect and remit for each such sale any tax imposed under section 12-408 , (B) be responsible for all obligations imposed under this chapter as if such marketplace facilitator was the retailer of such sale, and (C) in accordance with the provisions of subdivision (3) of section 12-426 , keep such records and information as may be required by the Commissioner of Revenue Services to ensure proper collection and remittance of such tax.

(2) The provisions of subdivision (1) of this subsection shall not apply to the facilitation by a marketplace facilitator of the rental of a passenger motor vehicle or rental truck on behalf of a rental company, as those terms are defined in section 12-692 .

(c) Any marketplace seller who is a retailer with a valid permit issued under section 12-409 shall not be required to collect the tax imposed under this chapter for a particular sale and shall not include the receipts from such sale in its taxable receipts for purposes of its return under section 12-414 , if: (1) The marketplace seller can show that such sale was facilitated by a marketplace facilitator (A) with whom the marketplace seller has a contract that explicitly provides that the marketplace facilitator will collect and remit sales tax on all taxable sales such facilitator facilitates for such seller, or (B) from whom such seller requested and received in good faith a properly completed certificate of collection certifying that such facilitator is registered to collect sales tax and will collect sales tax on all taxable sales by such seller and facilitated by such facilitator; and (2) any failure of such facilitator to collect the proper amount of tax for such sale was not the result of such seller providing such facilitator with incorrect information. The commissioner shall administer the provisions of this subsection in a manner consistent with section 12-410 and as if the language of said section had expressly referred to a certificate of collection under this section.

(d) Any purchaser of tangible personal property or taxable services who overpaid sales or use tax to a marketplace facilitator may submit a claim for refund with the commissioner in accordance with the provisions of section 12-425 , in such form and manner as the commissioner prescribes. No such purchaser shall have a cause of action against a marketplace facilitator for the recovery of any such overpayment under any provision of the general statutes.