flat income tax: if you earn more, you pay more tax, but it's still the same percentage, so "earn twice as much, pay twice as much tax" progressive income tax:

flat income tax: if you earn more, you pay more tax, but it's still the same percentage, so "earn twice as much, pay twice as much tax" progressive income tax: if you earn more, you pay more, but also a higher percentage, so something like "earn twice as much, pay three times as much" sales tax: spend twice as much, pay twice as much, a flat tax. it's not regressive, it's flat. "progressive" doesn't mean the political tendency, it means the tax rate progresses higher with income. A "politically progressive" sales tax, you might say, would change the tax rate on the basis of total spend, but difficult to implement because it can't be properly calculated at purchase time, unless you just want to make more expensive items have higher taxes, but you'd lose the tax efficiency described above for the VAT. now, it's not necessary to bend our thinking like a pretzel to try to make sales tax include an extra bonus for low income people (or extra burden for rich people) but why not just do that as part of progressive personal income tax?† and as discussed, fix sales tax with VAT... which we should simply call company income tax because that's what it is. † capital gains tax is interesting to discuss but not here, except to say "don't try to fix your problems with capital gains tax rates by making the sales, income, or VAT taxes crazy"