Legal Question in Business Law in California

Using a post office box, and even less so a forwarding service, are unlikely by themselves to render the forelign LLC subject to registration in California. However, the combination of the need or desire of the foreign LLC to have an address in California, the question of who will be collecting the mail from the P.O. box, and the apparent fact that you have a California Zip code all point to a likelihood that there are other factors that constitute doing business in California. Using a California address of any kind might also lead to someone investigating the LLC's lack of registration here, or to someone wanting to sue the LLC instituting the action here. So, all in all, the important thing is not what the LLC uses as an address, but where is it really handling its affairs. If the sole member lives in 91601, the LLC is doing business in California, period.