The bureaucrats have to still be involved (otherwise the system is violently and almost universally opposed), and most of the "flat tax / sales tax" systems still involve a "tax rebate" of some sort to insure that they will still be able to manipulate the system for income redistribution. Ironically, a lot of freepers couldn't see the problem with "rebates" that had nothing to do with the amount of tax actually paid (instead, providing a "rebate" based on the number of children, etc).