A (very) progressive tax rate with a few ways of reducing the tax based on social (e.g. number of children, etc) criteria would probably work better here.
So even when tiered, a person earning under some amount in total might get a lower tax rate than a person earning a higher amount but it is still flat.
The "flat tax" would be taxed on all jurisdiction. So call it a "universal flat tax". That way, there is no persuasion to register in a foreign country and it would dissuade multi geography registrations as you would just be taxed in multiples by each territory.
To avoid double taxation, perhaps, a company can register in multiple countries but since the tax is the same everywhere, the portion of the x% taxed would be proportionally divided to the territories.
This assumes of course that the whole world agrees on one tax policy and tax havens are eliminated. :)
They say there should be a 20% tax, on any income above the $35,000 a year threshold. While it still does effect people on the lower end more, the first part of their income is at least partially untaxed.
And the bar is low enough that the super rich will not be able to create schemes to keep there income under that bar.
Tell this to the nations which have successfully implemented a flat tax:
http://www.economist.com/node/3860731
https://en.wikipedia.org/wiki/Flat_tax#Countries_that_have_f...
It's ironic that a number of former Soviet countries have moved on to the flat tax, while the west has a progressive income tax (#2 plank of the Communist Manifesto).
Compare them to slowly declining western European countries like Italy and Spain.
People/politicians are very creative in what is to be considered essential.
For me personally - I would add one more change that most people don't like. I would put an actual cap on total income tax that can be paid in a single year. The reason for this is that these progressive systems act as a social welfare system that transfer money. That's why people propose a flat tax. Well, flat tax is much better but still presents the possibility for a wealthy person to pay, for example, 200k in income tax in a year. A lot of people would say "so what?". Well, I believe income tax shouldn't be treated as a maximum pain threshold. The basis of taxation is to fund public goods. We all consume roughly the same amount of public services on average. If someone is paying something like 200k a year in income tax they are paying way, way above anything they could possibly consume in public goods/services for that year.
But "no loophole tax" might be a better characterization of the flat idea, yes?
Maybe single means a complex function? I doubt it.
Remember that Flat Tax is also called Fair Tax. The concept of fairness is central.