Pollock overruled.
The Sixteenth Amendment removed the precedent set by the Pollock decision.
Professor Sheldon D Pollack at the University of Delaware wrote:
On February 25, 1913, in the closing days of the Taft administration, Secretary of State Philander C Knox, a former Republican senator from Pennsylvania and attorney general under McKinley and Roosevelt, certified that the amendment had been properly ratified by the requisite number of state legislatures. Three more states ratified the amendment soon after, and eventually the total reached 42. The remaining six states either rejected the amendment or took no action at all. Notwithstanding the many frivolous claims repeatedly advanced by so-called tax protestors, the Sixteenth Amendment to the Constitution was duly ratified as of February 3, 1913. With that, the Pollock decision was overturned, restoring the status quo ante. Congress once again had the "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".
From William D Andrews, Professor of Law, Harvard Law School:
In 1913 the Sixteenth Amendment to the Constitution was adopted, overruling Pollock, and the Congress then levied an income tax on both corporate and individual incomes.
From Professor Boris Bittker, who was a tax law professor at Yale Law School:
As construed by the Supreme Court in the Brushaber case, the power of Congress to tax income derives from Article I, Section 8, Clause 1, of the original Constitution rather than from the Sixteenth Amendment; the latter simply eliminated the requirement that an income tax, to the extent that it is a direct tax, must be apportioned among the states. A corollary of this conclusion is that any direct tax that is not imposed on "income" remains subject to the rule of apportionment. Because the Sixteenth Amendment does not purport to define the term "direct tax," the scope of that constitutional phrase remains as debatable as it was before 1913; but the practical significance of the issue was greatly reduced once income taxes, even if direct, were relieved from the requirement of apportionment.
Professor Erik Jensen at Case Western Reserve University Law School has written:
was a response to the Income Tax Cases (Pollock v Farmers' Loan & Trust Co.), and it exempts only "taxes on incomes" from the apportionment rule that otherwise applies to direct taxes.
Professor Calvin H. Johnson, a tax professor at the University of Texas School of Law, has written:
The Sixteenth Amendment to the Constitution, ratified in 1913, was written to allow Congress to tax income without the hobbling apportionment requirement. ... Pollock was itself overturned by the Sixteenth Amendment as to apportionment of income ...
