Most states require out-of-state businesses — not only Corporations, but often also Limited Liability Companies, Limited Partnerships, business trusts and other entities doing business in their jurisdiction — to obtain a Certificate of Authority and have a Registered Agent .

Different states have different definitions of just what "doing business" is. Virginia, for example, makes no effort to define the transaction of business in Virginia, since, per a former Virginia Code Commission, no inclusive definition seems possible.

Va Code §13.1-757(B) provides a non-exhaustive laundry list of the types of activities which may not of themselves constitute transacting business:

• hold board or shareholder meetings
• maintain, defend or settle any proceeding
• maintain bank accounts there
• have offices there for transferring, exchanging or registering of your own securities
• sell through independent contractors there
• solicit or obtain orders by mail, employees or agents, if the orders require acceptance outside the state before they become contracts
• incur debts there
• secure or collect debts there
• own, without more, real or personal property there
• conduct an isolated transaction there that can be finished within 30 days and not repeated
  

If you don't exactly fit a specific exemption, then you’re probably doing business in that state and must have a Certificate of Authority and a Registered Agent.