Before you can file any formation paperwork for your LLC, you need to choose a registered agent (sometimes known as a resident agent or statutory agent or by its acronym RA). A registered agent is a person or company that’s always available during business hours, every single day, to accept formal legal documents for your company in the unfortunate instance that you are sued.
Your LLC needs a registered agent in its home state (its domicile) and every other state in which it transacts business.
Most registered agents allow you to use their office address for all your mail and other correspondence. A good registered agent should also stay on top of your state filings for you and make sure that you remain in good standing in each state in which you are registered.
If you are registered in many states, this task can be onerous, so you’re better off leaving it to a professional service company or an attorney (a more expensive option).
Even if your state allows you to serve as your own registered agent, it's not a good idea. Unless you plan on being at your office during business hours every single day, without exceptions, and you have a good grasp of all the state filings that need to be done, you should leave it to the pros.
If you are not available when a lawsuit is served, you could lose the case by default — without knowing about it until it’s too late! Another consideration is that if you were sued, would you really want a process server or sheriff serving you a lawsuit in front of your customers?