The position that taxation is theft, and therefore immoral, is found in a number of political philosophies. Its popularization marks a significant departure from conservatism and classical liberalism, and has been considered radical by many as a result. The position is often held by anarcho-capitalists, objectivists, most minarchists, right-wing libertarians, and voluntaryists, as well as left-anarchists, libertarian socialists and some anarcho-communists.

Proponents of this position see taxation as a violation of the non-aggression principle. Under this view, government transgresses property rights by enforcing compulsory tax collection, regardless of what the amount may be. Some opponents of taxation, like Michael Huemer, argue that rightful ownership of property should be based on what he calls "natural property rights", not those determined by the law of the state.

Defenders of taxation argue that the notions of both legal private property rights and theft are defined by the legal framework of the state, and thus taxation by the state does not represent a violation of property law, unless the tax itself is illegal. Some defenders of taxation, such as socialist Matt Bruenig, argue that the phrase "taxation is theft" is question-begging, since it relies on presupposing a particular theory of property entitlement.

In the 17th century, John Locke took the position in Second Treatise of Government that government authority arises from the consent of the governed, and not through the divine right of kings. The libertarian activist L. K. Samuels, asserts in his "Rulers' Paradox" that since the citizenry is the holder of all rights, governmental bodies derive their authority to govern society via elections of government officials. In that vein, Samuels maintains that citizens can only give rights which they have. The Rulers' Paradox comes into play when governmental bodies exercise rights that the citizens do not hold or could not hold. According to Samuels: "If ordinary citizens could assassinate, steal, imprison, torture, kidnap, and wiretap without incrimination, that authority could be transferred to government for its democratic arsenal of policymaking weaponry." Taxation could be viewed as theft since, according to Lockean natural rights doctrine, government authority must obtain their rights from the citizenry.

Lysander Spooner, a 19th-century lawyer and political philosopher, who had argued before the United States Supreme Court, wrote the essay No Treason: The Constitution of No Authority. In it he stated that a supposed social contract cannot be used to justify governmental actions such as taxation, because government will initiate force against anyone who does not wish to enter into such a contract.

No open, avowed, or responsible association, or body of men, can say this to him; because there is no such association or body of men in existence. If any one should assert that there is such an association, let him prove, if he can, who compose it. Let him produce, if he can, any open, written, or other authentic contract, signed or agreed to by these men; forming themselves into an association; making themselves known as such to the world; appointing him as their agent; and making themselves individually, or as an association, responsible for his acts, done by their authority. Until all this can be shown, no one can say that, in any legitimate sense, there is any such association; or that he is their agent; or that he ever gave his oath to them; or ever pledged his faith to them.

The 19th-century French economist Frédéric Bastiat described taxes as legal plunder. Bastiat held that the state's only legitimate function was to protect the life, liberty, and property of the individual.

Now, legal plunder may be exercised in an infinite multitude of ways. Hence come an infinite multitude of plans for organization; tariffs, protection, perquisites, gratuities, encouragements, progressive taxation, free public education, right to work, right to profit, right to wages, right to assistance, right to instruments of labor, gratuity of credit, etc., etc. And it is all these plans, taken as a whole, with what they have in common, legal plunder, that takes the name of socialism.