On September 10, the Colorado Department of Revenue promulgated four sets of regulations related to remote sellers and marketplace facilitators. One set, adopts a special rule that establishes the sales tax requirements and conditions for sales made through a marketplace facilitator’s marketplace. A second set updates Rule 39-26-102(3) to clarify when a retailer is doing business in the state for state sales and use tax purposes. The other two published rules made conforming amendments to related administrative provisions, including an updated provision regarding the sales tax license requirement.