“Taxation is by definition legalized robbery. Clearly, it is initiated coercion. As such, no Objectivist can in good conscience support it. So, naturally, most of them don't. Ayn Rand, in her essay in The Virtue of Selfishness entitled "Government Financing in a Free Society," states emphatically that the financing of the state in a free society would be voluntary. But can it be?”

Voluntary Action (1948) Ch. 12

Source: Cannibals All!, or Slaves Without Masters (1857), p. 335

Page 42.
Sweet Tooth (2012)

Part I, Chapter III, The Problem of Conserving Surplus, p. 43 (italics as per text)
Storage and Stability (1937)

Source: The Illusion of Free Markets: Punishment and the Myth of Natural Order (2011), p. 32

Liberty and Taxation http://flag.blackened.net/daver/anarchism/tucker/tucker8.html
Individual Liberty (1926)
Context: Voluntary taxation, far from impairing the "State's" credit, would strengthen it. In the first place, the simplification of its functions would greatly reduce, and perhaps entirely abolish, its need to borrow, and the power to borrow is generally inversely proportional to the steadiness of the need. It is usually the inveterate borrower who lacks credit. In the second place, the power of the State to repudiate, and still continue its business, is dependent upon its power of compulsory taxation. It knows that, when it can no longer borrow, it can at least tax its citizens up to the limit of revolution. In the third place, the State is trusted, not because it is over and above individuals, but because the lender presumes that it desires to maintain its credit and will therefore pay its debts. This desire for credit will be stronger in a "State" supported by voluntary taxation than in the State which enforces taxation.

Address accepting the Presidency of the Congress of Industrial Organizations, Atlantic City, New Jersey, December 4, 1952, as quoted in Walter P Reuther: Selected Papers (1961), by Henry M. Christman, p. 51
1940s, Address accepting the Presidency of the CIO (1952)
I've often thought: Why is it that you can get a great nation like America marching, fighting, sacrificing, and dying in the struggle to destroy the master race theory in Berlin, and people haven't got an ounce of courage to fight against the master race theory in America? We need the same sense of dedication, the same courage, and the same determination to fight the immorality of segregation and racial bigotry in America as we did in the battlefields against Hitlersim.

Ideas That Kill http://www.city-journal.org/html/10_1_diarist.html (Winter 2000).
City Journal (1998 - 2008)

Murray Rothbard, The Anatomy of the State, Auburn, Alabama, Mises Institute (2009) p.11, first published in 1974 https://mises.org/library/anatomy-state