On December 1, 2018, Connecticut and Colorado will be enacting and immediately imposing economic nexus standards. At a high-level, here is an explanation of each state's economic nexus thresholds.
Colorado - Companies with gross sales of at least $100,000 or greater OR 200 individual transactions in Colorado during the previous or current calendar year have established economic nexus. These companies must register to collect and remit sales tax (grace period in effect until May 1, 2019). During the grace period, non-collecting retailers that have exceeded the thresholds must still comply with Colorado’s notice and reporting regulations.
Connecticut - Companies with gross sales of $250,000 or greater AND 200 individual transactions in Connecticut during the previous 12 month period ending on September 30 have established economic nexus. Connecticut requires companies to determine whether the thresholds have been met on a an annual basis ending September 30. Companies that have established economic nexus must register to collect and remit sales tax.