[C19fan]

16th Amendment:

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.

Where is the clause about uniformity?

[Jacquerie]

Article I, Section 8:

“. . . but all Duties, Imposts and Excises shall be uniform throughout the United States.”

[sourcery]

SCOTUS correctly held that "Sixteenth Amendment conferred no new power of taxation but simply prohibited the previous complete and plenary power of income taxation possessed by Congress from the beginning from being taken out of the category of indirect taxation to which it inherently belonged. [240 U.S. 112 (1916)]". The income tax always was and is Constitutional as an excise tax under Article I, section 8 of the orginal Constitution ("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.")

The effect of the 16th Amendment was simply to undo the wrongful SCOTUS decision in Pollock.