Sure, NIT + control of income tax rates is isomorphic to UBI + control of income tax rates in terms of how much money people get in a year. The core downside of

Sure, NIT + control of income tax rates is isomorphic to UBI + control of income tax rates in terms of how much money people get in a year. The core downside of piggybacking on the existing tax refund system is that individuals would get their NIT refund once per year, and spiky distribution has problems. One of the core benefits of NIT/UBI is that many inefficient means-tested welfare programs could be ended without people starving, going homeless, using the ER as healthcare, etc. But if the distributions are a year apart plenty of people are going to exhaust their money and require those welfare programs to continue, now all the more inefficient because the relevant population in smaller. NIT has to be tabulated based on income, but UBI can be monthly/weekly/daily/whatever frequency.