Eliminate all deductions, exceptions, and other loopholes.
Let's say the tax rate was set at 5 per cent of income.
So if your income is $20,000, you pay $500.
If $200,000 income, your tax is $10,000.
If you have $100 million in income, your tax is $5 million.
End of story. 5% might be too high though!
I’ve seen calculations that put the percentage at 17% to be revenue neutral.