The USA has about 1/3 of billion people. The current poverty level is less than$15k for s single person . Making 15k the UBI yields $5 trillion in transfers. Current US GDP snd Personal income is about $24 trillion. So $ 5 trillion is arithmetically available.
Of course, there are various current transfer programs (disability, part of social security, food stamps, etc…) that would no longer be needed. And depending on the household size and earned income, some UBI would be taxed. A conservative estimate of those savings is at least 1/2 trillion. Yielding a net revenue need of 4.5 trillion. It is certainly in the realm of non-destructive taxation to this observer.
Of course, it would require major legislative overalls of many programs and the tax code.
Thanks for a starting point
With respect to your premise...
- Why would you tax UBI? That seems like double-dipping, and kind of defeats the purpose. Or is this just short-hand language, and you actually mean that for some people, the UBI would push their income above the 0% bracket, so that previously untaxed incomes would now be taxed?
- Why choose FPL? FPL doesn't provide a livable income except perhaps in a very few places in the US.
- Are you assuming that the workforce will remain unchanged in future years? Are you assuming that nobody will choose to no longer work? At a minimum, I would think that at least some families will decide that it's more advantageous for one parent to stop working and stay home with the kids, and that would impact the taxable base in future years.
My biggest problem with your example is that the math only works because you're using the ENTIRE GDP as your base. Your estimate using FPL, with offsets for sunset welfare programs, results in a need for $4.5 trillion.
In 2022, the entire government revenue was just a bit over $5 trillion. To make your premise work, your basically assuming an increase to the tax rate of 25% across the board from it's present levels, for all taxes of every type.