I know NY is one that wants everyone to have a preparer registration number....CA only has something special if you work IN California.   

I saw something about Oregon changing their requirements, and out of state preparers may need something special, but I "think" thats only if you solicit yourself to OR residents...all my OR clients came to me originally as  CA residents first, then moved at some point, I dont solicit to anyone outside of the state of CA.