The notion that taxes are unconstitutional and not mentioned in the US Constitution is, like most propaganda, not true. It isn’t even a little white lie, it’s a great big whopper.
The Tax and Spending clause of the US Constitution reads:
The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defense and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States;
So one of the enumerated powers granted Congress is:
The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises
There are some limitations on taxation as well. The Originating Clause says that all spending bills must originate in the House of Representatives. There are requirements for the apportionment of direct taxes and for indirect taxes being levied uniformly.
However, the 16th Amendment made some changes to the above. Just so there would be no squabble about the meaning of the above mentioned clauses, it states:
The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration.
It goes on to further define this taxing power:
Article I, Section 2, Clause 3:
Representatives and direct taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers…
Article I, Section 8, Clause 1:
The Congress shall have Power to lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States.
Article I, Section 9, Clause 4:
No Capitation, or other direct, Tax shall be laid, unless in proportion to the Census or Enumeration herein before directed to be taken.
This clause basically refers to a tax on property, such as a tax based on the value of land, as well as a capitation.
Article I, Section 9, Clause 5:
No Tax or Duty shall be laid on Articles exported from any State.
Article I, Section 8. Transcript of the Constitution of the United States)
Notice that last part? “…[A]ll Duties, Imposts and Excises shall be uniform throughout the United States…”? That clause is what initially did not permit Congress to pass income taxes, for the simple reason that incomes vary widely around the country.
But that’s not the end of the story, and the Sixteenth Amendment to the United States Constitution was adopted authorizing the collection of income tax without apportioning it among the states or basing it on the Census. The amendment was adopted in 1913, so it’s long-settled law at this point.