Everyone gets paid a minimum subsistence wage - say $15,000. This is paid only into bank accounts and in a gradual fashion to reduce the chance of the financially unsophisticated blowing their money too fast.

Everyone is free to work as much or as little as they see fit. They get to keep every dollar they earn (legally).

All purchases attract a VAT of 30%.

For a population of 250 million, the cost of the subsistence wage is $3.75 Trillion. If the economy is bigger than $14 Trillion, the government makes a profit and can begin to pay other burdens such as the cost of government and the army, but no longer needs social security except for the tiny fraction of people who are genuinely mentally inadequate to live in a modern society or are too ill to survive on the subsistence wage.

For those not prepared to do the math, this sort of reverse taxation works exactly the same as a progressive tax with social security, but based on consumption, not earnings.

You could also run a flat-rate 25% tax on all earnings - both income and capital gains and avoid consumption taxes. With everyone registered for the subsistence wage, and mandates that all wages must be paid direct bank accounts, you begin to clamp down on the black economy. [Oh, I should explain a few points here - that may not come over so well in USA speak - in most of the world, the "black economy" is the undeclared portion of the economy that doesn't go through accounts books and isn't declared for tax, yet is based on "normal" activities rather than explicit illegalities. I'm also not so naive to beleive that the black economy will magically go away because someone says "boo" to it. There is a powerful temptation to ordinary people to do something off the books and save tax. However, with everyone having a bank account and with adequate electronic tracking of money transactions [Yes, Big Brother is watching!], then this can be reduced to the benefit of the law-abiding majority)

It would be nice if you could get away with tax at the 10% level, but you can't, IMHO. A modern society needs too much infrastructure and support. You could get away with 10% if you went "user pays" across the board, but you would have to start billing individuals for the existence of the army.

You might want to go play here. It doesn't have reverse taxation, but it gives you an idea of the relative scale of different sectors of the US economy and the budget outlays by category.