In his March 20, 2002 letter to the Wall Street Journal "'Tough-Guy' Proposals for Indiana's Budget," that state's Governor Frank O'Bannon calls "for increases in two minor, voluntary taxes - on cigarettes and riverboat admissions."
"Voluntary taxation?" "Voluntary taxation" is an oxymoron if ever there was one; it is similar to "jumbo shrimp," "an important trifle," or "a square circle." "Voluntary taxation" is a downright contradiction in terms, since if there is anything that taxation is not, it is voluntary. The proof is, if you do not pay, your property is forcibly confiscated and/or you go to jail. "Coercive taxation" is a redundancy, because once you comprehend the latter word in this phrase, you know the meaning of the former is a constituent part of that understanding.
This is but one - though a typical one - example of the way politicians abuse the language in attempting to deceive the people about the true nature of their actions.
Does the good governor mean that purchasers of cigarettes/entrants onto riverboats don't have to pay the relevant tax if they don't want to? Or does he mean that they don't have to pay the tax if they don't buy cigarettes/enter riverboats? It is not likely that he intends the former. If the latter, then, of course, all taxes are voluntary; e.g., one could avoid property taxes on residential property or sales taxes on food merely by going homeless or not buying food, respectively. In the latter case, perhaps one could survive by foraging in dumpsters. Similarly, he might mean that income taxes are really voluntary, in that you can choose not to earn an income, in which case you are not subject to the tax. That is, because voluntary choice determines whether or not a tax applies, the levy in question is not really compulsory.