Two things to keep in mind: 1) Even if the marginal tax rate is fairly high, your average income earner will be getting that $18000 back in UBI which makes the

Two things to keep in mind: 1) Even if the marginal tax rate is fairly high, your average income earner will be getting that $18000 back in UBI which makes the effective rate in your scenario more like 5%. 2) The majority of tax revenue comes from the highest earners. A quick google gave me this (from https://taxfoundation.org/summary-latest-federal-income-tax-data-2015-update/ https://taxfoundation.org/summary-latest-federal-income-tax-...): The top 1 percent (1.3 million filers) paid a greater share of income taxes (37.8 percent) than the bottom 90 percent (124.5 million filers) combined (30.2 percent). In other words, I don't believe your math is a reasonable approximation of how the budget would work out. If everyone pays the same effective rate as today (including welfare and other social program recipients who can be treated as having a negative effective rate), nothing changes. Also, there is no need to presume a flat tax rate; the U.S. does not have a flat tax rate, now. EDIT: Also the average household size in the U.S. is 2.53 people, not 4. A naive calculation would suggest that a household of 4 should therefore expect a mean income around $83K.