He changed his primary address on all of his bills, bank statements, credit cards, etc. to his Nevada address.
I've told him that he would probably be safe ignoring the threats of the State of Utah (I'm not a tax attorney, but I remember learning things in tax law that I've forgotten by now that gave me the impression that this wasn't OK), but he fears two things: 1) being audited, 2) having to front the court costs to fight it.