The equitability of a basic income is not its main selling point, as I see it; in other words it is not necessary that it be equitable according to some specific conception in order for a basic income to provide value to society as a whole. The selling points are, as I see them:

- There are now more people spending money because they have disposable income. This is good for businesses.

- There is added incentive to work, because one does not lose income by starting a job.

- The people being made redundant by automation are given a cushion that will help as they figure out how to become economically relevant again. This is good for everyone, because there are fewer families forced out onto the streets, etc.

- There is, potentially, less of a bureaucracy to manage the distribution of existing welfare programs, assuming existing programs can be consolidated into the new basic income scheme. This is an attractive point for conservatives and libertarians.

There's no need for equitability here, although that's also something that is desirable within bounds. But I think few millionaires and billionaires will find a significant decrease in their standard of living if they have to pay more into the pot than they receive. Also keep in mind that the billionaires are billionaires because society provides a framework for them to accumulate and retain the capital that they have; for this reason they have an implicit debt and obligation to society.

Equitability is not absolutely necessary, but it is a great selling point.

With a scheme like this, one would replace a system full of loopholes (for the rich) and handouts (for the poor) with a simple flat system.

Everybody gets $x/yr, and everybody pays y% in taxes on all income after that (not just earned income). No deductions, no credits, no loopholes, no welfare state (other than the UBI).

For some people this "mincome" would be theirs to spend, but for others it'd just be a minor reduction in income taxes.

What's somewhat clever about this is how it essentially balances out. The billionaire won't even notice the extra amount in their bank account, but there aren't many billionaires. Meanwhile the three jobs four kids single mom will be greatly impacted by this, which is the whole point.

The billionaire won't notice it because it won't exist; the billionaire will be taxed way above mincome, because otherwise how are you going to pay for it?

That's exactly the purpose of basic income. If a billionaire businessman replaces all of his workers with robots, all of his income goes directly to him. The laid off employees are now competing for the few jobs that are available which have not yet been automated, and not all of them will be able to find another job because other businesses are automating away humans too. We need a way to redistribute wealth from the billionaires who make their money off the efficiency of automation to the people who would have previously worked for them.