That's right. A voluntary tax, just like the lottery.
The thing is, most people will actually buy more goods and pay more taxes once the FairTax is implemented because once the price of goods settles out, as per the book, people will have more disposable income because the gubmint ain't snatching 20-50 percent and it will be a boost to the economy as well as tax receipts.
BTW, I write my congress critter, RINO Graham, periodically and the last time I wrote was about the FairTax. I got a letter back from him yesterday saying that he supports a '8.5%' sales tax. Have you heard of this?
That almost sounds like a state sales tax rate. You might double check with him on what he really meant.