The Sixteenth Amendment is the constitutional basis for the modern federal income tax. Ratified on February 3, 1913, it allows Congress to lay and collect taxes on income "from whatever source derived" without dividing the tax among the states by population. Before it, the Supreme Court had treated a federal income tax as a direct tax that had to be apportioned, which made a broad income tax impractical.
The Text of the Sixteenth Amendment
The amendment reads: "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."
The wording is short, but it changes two rules at once. It removes the apportionment requirement and removes any need to tie the tax to a census count.
The Problem the Amendment Solved
The Constitution divides federal taxes into direct and indirect taxes. Direct taxes, historically including taxes on land and capitation taxes on persons, must be apportioned among the states according to population. Indirect taxes, such as duties and excises, need only be uniform throughout the country. In Pollock v. Farmers' Loan & Trust Co., 157 U.S. 429 (1895), the Supreme Court struck down a federal income tax, holding that taxes on income from property were direct taxes and had to be apportioned. Apportionment by population would have produced wildly unequal burdens, so a broad income tax could not work under that rule.
The Sixteenth Amendment removed that obstacle. It does not create the income tax by itself. Congress still has to pass a tax law, and it did so with the Revenue Act of 1913, which imposed the first permanent peacetime federal income tax under the new amendment.
What the Amendment Does and Does Not Do
| It does | It does not |
|---|---|
| Allow Congress to tax income without apportionment | Create the income tax directly |
| Reach income from any source | Set rates, brackets, or deductions |
| Remove the census requirement | Limit state income taxes |
| Support a uniform tax nationwide | Eliminate other constitutional limits |
What Counts as Income
Courts have read "income" broadly. In Commissioner v. Glenshaw Glass Co., 348 U.S. 426 (1955), the Supreme Court described taxable income as accessions to wealth, clearly realized, over which the taxpayer has complete dominion. That definition reaches wages, salaries, business profits, interest, dividends, rents, and many other gains. The Internal Revenue Code, at Title 26 of the United States Code, supplies the detailed rules, including what is included, what is excluded, and what is deductible. The code is published at govinfo.gov and congress.gov.
Some people argue that wages are not income or that the amendment was never properly ratified. Federal courts have rejected those arguments repeatedly, and the Internal Revenue Service lists them among frivolous positions that can lead to penalties. Understanding the amendment as a grant of taxing power, not a limitation on what income means, is the accurate reading.
The Income Tax and the Taxing Power
The amendment sits alongside other taxing clauses in Article I, Section 8, which allow Congress to lay taxes to pay debts and provide for the common defense and general welfare. The income tax is one form of that power. The amendment did not repeal the uniformity requirement for indirect taxes, and it did not authorize taxes that violate other constitutional guarantees, such as the right to due process or equal protection.
In Brushaber v. Union Pacific Railroad Co., 240 U.S. 1 (1916), the Supreme Court upheld the 1913 income tax against a challenge that the amendment conflicted with the Constitution's other tax rules. The Court treated the amendment as clarifying that income taxes are not subject to apportionment.
Federal and State Income Taxes
The Sixteenth Amendment applies only to Congress. States have their own taxing authority under their constitutions, and most states impose an income tax under state law. Some states have no income tax at all. A state income tax does not depend on the Sixteenth Amendment, and a challenge to a state tax generally turns on the state constitution, not the federal one.
Enforcement and the IRS
Congress created the Internal Revenue Service to administer the tax code. The agency issues regulations, publishes guidance, and audits returns. Tax crimes, such as willful evasion, are prosecuted under federal law. In Cheek v. United States, 498 U.S. 192 (1991), the Supreme Court held that a good-faith misunderstanding of the tax law can defeat the willfulness element of certain tax crimes, though an unreasonable belief that the law is unconstitutional does not count.
How the Amendment Was Adopted
Congress proposed the Sixteenth Amendment on July 12, 1909. The proposal moved through Congress as a narrower alternative to a more sweeping tax plan, and it was framed as a fix to the apportionment problem rather than a full tax program. The states ratified it over the next several years, and the amendment was declared part of the Constitution on February 3, 1913. Congress passed the Revenue Act of 1913 later that year, and the modern income tax began.
Common Misconceptions
Several myths about the amendment circulate widely. Courts and the Internal Revenue Service have addressed them many times.
- That the amendment applies to the states. It does not. It grants power to Congress, and state income taxes rest on state law.
- That wages are not income. Courts read income to include compensation for work, and they have rejected the argument that wages fall outside the tax base.
- That the amendment was never ratified. The ratification was certified in 1913, and federal courts treat challenges to its validity as frivolous.
- That the amendment limits how much Congress can tax. It removes an apportionment rule; it does not set a ceiling on rates.
Why the Amendment Still Matters
Every debate over tax rates, deductions, credits, and the scope of the tax base plays out against this short amendment. It settled that the federal government can raise revenue from income directly, without the cumbersome apportionment rule, and it gave Congress room to build the system that funds much of the federal government today.
This guide is general information about the law and is not legal advice. Tax questions depend on the taxpayer's facts and current law, and anyone with a real tax issue should consult a licensed tax professional or attorney.