Basically, in the US, if you have a mailing address that can be where you "live." It may not be able to be a PO Box and, if you're a politician or otherwise high profile, someone may look into it. But if you're an ordinary Joe and you have a trusted relative/friend who will keep an eye out for important mail, that's mostly fine. A state could get cranky if they think you owe them taxes but mostly they'd have no way of knowing. You may need to do the odd thing in person but it's mostly very informal.