Reddit reviews Fair Not Flat: How to Make the Tax System Better and Simpler

Not a direct answer to your question, but related. In Fair Not Flat, the author proposes an alternate approach to executing a consumption tax. He states that:

Income = Consumption + Savings

So Consumption would be Income - Savings.

Essentially, you'd leverage the existing tax approach, and be taxed on everything that wasn't put into special savings accounts.

The book contains a lot of details about what deductions would be kept or gotten rid of, as well as some specific suggestions for rates, but the gist is that a consumption tax doesn't necessarily have to be a sales tax.