More information can be found in CIRCULAR LETTER OF INTERNAL INCOME NO. 20-40 (“CC RI 20-40”).
From the announcement (translated from Spanish):
Section 4010.01 (ddd) of the Code defines the term “Market Facilitator” as any person who facilitates the sale of tangible personal property, specific digital products or taxable services through a market in a medium that could include a store, counter, catalog, website or some other medium of a similar nature. A Market Facilitator is obliged to collect the SUT in all transactions carried out in its market, regardless of whether the sale is a direct sale by the Market Facilitator or is a sale made by another person through said Market Facilitator.
On the other hand, Section 4010.01 (eee) of the Code defines the term “Market Seller” as a seller who makes retail sales through any physical or electronic market, operated or controlled by a Market Facilitator, even though said seller would not have had the obligation to collect the SUT if his sales had not been made through said market. In other words, a Market Seller can be a merchant registered in Puerto Rico, or it can be a person who is not registered as a merchant in Puerto Rico.
Article 4010.01 (iii) -1 (b) (1) and (2) of the Regulation include several examples of when a merchant is considered a Market Seller.
In addition, a merchant dedicated to the sale of taxable items in Puerto Rico who, in addition to having his business premises or website to offer his products to residents of Puerto Rico, sells his products through a Market Facilitator, is also considered a Market Seller, exclusively with respect to transactions for the sale of taxable items that are carried out through the Market Facilitator.
According to the provisions of Section 4020.08 of the Code, all those transactions that constitute sales dispatched by mail will be subject to the collection of the SUT regardless of whether the seller is a merchant. In these cases, it will be considered that the sales made by mail will be subject to the collection of the SUT as long as they are made by a Market Facilitator. In these cases, said Market Facilitator will be considered the withholding agent and will be obliged to collect the SUT and remit the tax collected to the Department on behalf of the Market Seller.
In the case of Market Sellers who are merchants duly registered in SURI, they will not have the obligation to collect the SUT in those sales transactions of taxable items that are carried out through Market Facilitators. However, in order to be entitled to such relief from the obligation to collect and remit the SUT, the Market Seller must obtain a Collection Release of Sales and Use Tax from the Market Seller (“SUT Collection Release”) as provided provided in Article 4020.05-4 of the Regulations and in accordance with the procedure established in Part III-C of this Circular Letter.