Boortz's response to a near identical question:
It's illegal now .. it will be illegal then. That same tax avoidance scheme is available to you right now. Why don't you get out there and try it? Let us know how it works out.
Right now there is a compliance method, I have to keep records and fill out forms and defend my expenses. Under the Fair Tax, since all the savings are coming by getting rid of compliance expenses, and there is no IRS to come after me, what would catch the person who cheats the system?