Actually the Fair Tax was written to include a "pre-bate" where below a certain income level you receive a check for the average amount you would pay in tax for the month on "basic necessities". Or something along those lines, it's been a long time since I've read about it so my memory is hazy.
I never liked this idea and would rather see a system where you simply don't charge the tax on basic necessities. I would think that modern database systems used in stores and modern computing power would allow the government to very quickly and easily set that up. Or at least as quickly and easily as the government could work. It would be a case of needing to set guidelines for what is and what isn't a "basic necessity"