Most proposals don't remove the limit. They would tax income from 0 to X, not tax it from X to Y, and then tax it again for income over Y. Hence you get a "donu

Most proposals don't remove the limit. They would tax income from 0 to X, not tax it from X to Y, and then tax it again for income over Y. Hence you get a "donut hole" of untaxed income in the middle. I can think of no economic justification for such a proposal, though it's clear why it would be politically palatable. But that's exactly where complexity comes from: political compromises.