Earlier quoted context omitted.
It's 21% for FY 2016 (which is a percentage based on including social security and medicare, which as I mentioned, are not part of federal income tax receipts; the percentage ). 2017 isn't done yet; I'm not using an estimate with an administration going sideways. https://en.wikipedia.org/wiki/Military_budget_of_the_United_... "Military budget of the United States. ... The budget funds 4 branches of the U.S. military:…
OK, that is bizarre; visit usgovernmentspending.com site on mobile and the chart says US FY2016 spending on Defense is 17%. On desktop, the chart says 21%.... In any case, as a percentage of federal income tax it does seem that defense is around 25%. "U.S. discretionary spending" is simply spending which is authorized annually instead of authorized by laws spanning multiple years. It doesn't seem to be a highly meani…
So that's not entirely how income vs payroll taxes work.
If you get a paycheck, out comes taxes for social security and Medicare. There is an annual limit on how much of your income is taxed for social security, whereas there is no limit for Medicare, and there's a bump in the Medicare rate after a very high dollar amount (near $250k/year if I recall). For our argument, none of the above is refundable (if you pay too much social security tax because of multiple W2 employers, the extra tax gets applied to your federal income liability).
For income tax, lots of people pay through their paycheck, although if you're below a certain yearly income threshold, federal income tax is not withheld (you even get a refundable tax credit for working if you're poor enough). Also, as you mentioned, capital gains taxes also are federal income tax revenue. So, income tax is not unearned income alone.