Could I, hypothetically, go through all of the paperwork to set up a "shell LLC" and use that as a cover to make all of my household purchases tax-exempt?  Sure, in theory.  But sooner or later someone's going to notice that I'm making some purchases that seem awfully odd for a company, and that there isn't any business volume coming across my books.  This will be followed by a visit from "Uncle Andy" (or whoever's serving as the State Treasurer at the time), with some questions that I don't have answers to.  The next thing you know, I'm getting fitted for a prison jumpsuit.