We actually had voluntary tax in Montreal in the 60s. Mayor Jean Drapeau, who brought us the Metro, Place Des Arts, the 1967 World's Fair, and more, needed a way to finance it all. So he created a lottery, which was quite illegal, and he knew it. To get around this, he called it a Voluntary Tax - people donated two bucks with the expectation of absolutely nothing in return. Except for one lucky winner every week.It worked for a couple of months, until the federal governemtn called his bluff.

I guess this is a joke, but in case it's not:

There are good reasons why taxes are compulsory, basically to do with the proper functioning of society! The concept of "voluntary taxes" is nonsense. "Charity" is the word you're looking for - and we already have that!

actually its only partially a joke. I meant to say that we still pay the normal taxes that we pay, but it anyone thinks that their bracket should be paying more, they are free to do so.

USA Tax forms (I think) have a line:

"contribute $________ to national debt reduction".

Free-rider problem. Its why taxes cannot be voluntary.