I haven't had the opportunity to crunch the numbers. He intends it as a transitional step to the Fair Tax, where we eliminate income taxes and switch to a national sales tax, with a check sent to every American household to cover basic living expenses.
It has some strong points--the middle class and working class are struggling badly while the federal government continues to burden them with taxes and mandates that squeeze their budgets. 9% would help everyone. Smaller business taxes would help us be more competitive with other countries in an increasingly globalized economy.
I can see a few downsides, though.
1) A national sales tax needs to exempt groceries and medicine. Those are basic needs and a 9% tax on them would be just as much of a burden on people at the bottom as our current system. Sales taxes should fall only on non-essentials...that way, if you can afford to buy the non-essential item you're not being hurt by a tax. It's something you want instead of something you need.
2) A flat tax on business is unrealistic. The tax code still has to define what is and isn't a legitimate deductible expense, so there won't be anywhere near the simplification advertised. And you can't have a tax on gross receipts because different industries have vastly different profit margins.
3) If you send every household a check, you're wasting a lot of money no administrative costs, and you're giving money to everyone including Bill Gates. If you means-test, you still have to maintain the IRS, require people to file taxes, require businesses to report payments to employees and contractors, etc. So you have two bad choices on that provision.
