Then many (the upper half of?) citizens will have tax burdens greater than their basic income payments.

Is it “not means tested” because you and the IRS both mail each other checks instead of using net settlement?

What makes UBI different from standard progressive taxation and welfare?

Most (all current?) welfare schemes have a disincentive for work because earning income disqualifies you from welfare, and getting a poor job can make you worse off even if the welfare amount is below the minimum wage, since going to that job often also does add extra expense (transportation, caretaker for kids and other dependents, etc).

With unconditional basic income, however, all the job income is extra, which is a big difference in motivation especially for people who can't hold a full-time job because of health issues or having to take care of others.

Furthermore, standard welfare systems don't handle structural unemployment well - they don't provide a long-term (decades, not months or years) means of support to able-bodied people that can't get a job. Historically, that wasn't much of a problem - able-bodied people could get a job if they really wanted most of the time; if there was an economic slump, then it went away in a couple years (and welfare could help ride it over), and if they couldn't get a job, then retraining was a solution. In the future, the situation is different, we should expect millions of people, eventually a majority of population, whose labor is economically unnecessary (it can be done by machines better if these people aren't allowed to participate) despite any reasonable retraining. This issue is(will be) new, and current methods clearly won't work.

People respond to "carrots and sticks", and UBI brings a much more sensible set of "carrots and sticks" than progressive taxation + classic welfare.

>all the job income is extra

If a realistic working person's income tax liability is going to be a substantial portion of or greater than the UBI allocation, UBI is really just unemployment insurance and the disincentive to work remains.

We already have a "basic income" for working people: (personal exemption + standard deduction) * (marginal tax rate). Working people are still net taxpayers. Making them not net taxpayers is just sharply increasing the progressiveness of the progressive taxation scheme, i.e. standard liberal/Democratic politics since forever.

I'd support reframing the standard deduction, personal exemption, child tax credit, etc. as refundable credits, but this is only "income" at the bottom of the distribution.