Connecticut

Foreign entities may not transact business in this state until they register with the Connecticut Secretary of State. It is not considered transacting business if a company is:
1) maintaining or defending a lawsuit;
2) carrying on an activity concerning internal affairs;
3) maintaining bank accounts;
4) maintaining an office for the management of an entity’s own securities;
5) selling through independent contractors;
6) soliciting or obtaining orders that require acceptance outside of the state before they become contracts;
7) creating or acquiring indebtedness in real or personal property;
8) securing or collecting debts;
9) owning, without more, real or personal property;
10) conducting an isolated transaction completed within 30 days; or
11) transacting interstate commerce.

This list is not exhaustive but Regulations of Connecticut State Agencies provides, somewhat contradictory, clarification where it provides that, for purposes of business tax nexus, a company is “carrying on business in this state” if it 1) owns or leases real or personal property; 2) maintains an office or compensates an employee to work from home; 3) sells tangible personal property; 4) performs or solicits orders for services; 5) sells or solicits orders for real property; 6) maintains inventory in a public warehouse or employee’s home; 7) has employees within the state; 8) delivers merchandise inventory on consignment; or 9) participates in the approval of servicing distributors and dealers where a customer will have such product serviced or repaired.

200 or more retail sales into Connecticut and $100,000 in gross receipts from sales in Connecticut.