Colorado

Generally, an entity conducting business in the state must register as a foreign entity. 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;
11) transacting interstate commerce; or
12) creating or acquiring mortgages or other security interests in real or personal property.

This list is not exhaustive and is not overly descriptive but the Colorado Department of Revenue provides that “in general, a retailer is doing business in Colorado if the retailer sells, leases, or delivers tangible personal property.”

Sales of over $100,000 in products or taxable services in a calendar year.