According to a FactCheck.org analysis of the Fair Tax (as proposed by presidential candidate Mike Huckabee in 2007):
We stand behind our earlier analysis of the FairTax. The proposal to which Gov. Huckabee referred is not a 23 percent tax, but rather a 30 percent tax. And it is revenue-neutral only through an accounting trick. It will collect more money from those earning between $15,000 and $200,000 per year and less from those earning more than $200,000 per year. It is possible that the FairTax would make most people better off, but much of that gain would be a direct result of making the tax code less fair.