In what manner is taxing basic income anything other than a full-employment programme for bureaucrats? Surely it costs less in total to pay someone $10,000 a year than to pay them $12,000 and oblige them to fill out a (probably error-filled) income tax return, pay $2,000 in taxes, and have to process all that paperwork, payments, refunds, audits, etc. Same arguments apply to SSRI and other similar schemes. Just make it nontaxable and then if someone had no other significant sources of income they just do nothing.

As a matter of policy, I'm all for broadening the tax base, ideally to 100%. But that makes zero sense in concert with BI.

I'm not sure who proposed the thing you're arguing against here, or precisely the shape of it. Clearly many people receiving BI would still be filing taxes, as everyone receives a BI by the definition of a BI. I can think of some reasons we may want to treat BI as income like any other income.

I think we'd definitely want to count BI as income in general, but we may want to rework the tax code on the low end such that if BI is your only income you don't need to file, as fredkbloggs suggests. One way to do so might be setting the standard deduction equal to BI and eliminating refundable tax credits.

I can also see introducing BI as an opportunity to remove some of the tax expenditures that riddle the tax code -- broaden the tax base. But I don't see any reason to change the basic nature from progressive to flat. After all we'd still need to raise quite a bit of money to pay the BI as well as the remaining government functions that BI doesn't replace. Even under the current progressive model, eliminating tax expenditures is probably not going to be enough.

That could certainly make sense.

One argument I see for making them file anyway is reducing disincentives to work; I'm not at all sure the magnitude of that disincentive is worth the extra paperwork, though.

Yeah I haven't heard anyone suggest a flat tax in conjunction, but social security and unemployment could be eliminated, food stamps cut sharply, Pell grants all but eliminated, and so on. I'd conservatively estimate that a trillion of the $2.8 trillion cost could be offset through reduced social spending elsewhere. Another $600B or so would come back to the government in the form of income taxes. So net you are looking at $1.2T. No question, that's a lot of money but it's not far off from the size of the MIC. It's a choice that could be made.

I don't know how to quantify, but I have definitely heard proposals for BI with a flat tax and with a progressive tax, with somewhat different groups pushing them.