The Sixteenth Amendment to the U.S. Constitution gives Congress the power to lay and collect taxes on income “from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration.”1Congress.gov. US Constitution – Sixteenth Amendment Ratified on February 3, 1913, it is the constitutional basis for the federal income tax. In thirty words it removed the single legal obstacle that had blocked a national tax on earnings, and it is the reason the IRS, graduated tax brackets, and the return you file every April exist in their current form.
Why the Amendment Was Needed
Before 1913, the federal government funded itself mostly through tariffs and excise duties. Congress had tried to tax income directly, most notably with an 1894 law imposing a 2 percent tax on corporate and individual incomes above $4,000.2U.S. Capitol – Visitor Center. HR 5442, A Bill to Impose a Tax on Corporate and Individual Incomes, January 24, 1894 The tax lasted barely a year. In 1895, the Supreme Court struck it down in Pollock v. Farmers’ Loan & Trust Co., ruling 5–4 that taxes on income from real estate and personal property (rents, dividends, interest) were direct taxes that the Constitution required to be apportioned among the states by population.3Library of Congress. Pollock v Farmers Loan and Trust Co, 157 US 429 (1895) Because those provisions couldn’t be separated from the rest of the statute, the whole income tax fell.
Apportionment came from Article I, Section 9, which forbids any direct tax “unless in Proportion to the Census or enumeration.”4Congress.gov. ArtI.S9.C4.1 Overview of Direct Taxes In practice this meant a state with 10 percent of the national population had to supply 10 percent of the total revenue collected. That math is workable for a head tax and ruinous for an income tax. A wealthy state with a small population would face sky-high per-person rates, while a populous but poorer state would face almost none. No coherent national income tax could survive that rule, and after Pollock, changing the Constitution was the only route forward.
Congress approved the proposed amendment in July 1909 and submitted it to the states.5History, Art & Archives – U.S. House of Representatives. The Ratification of the Sixteenth Amendment Three-fourths of the state legislatures (36 of the 48 states then in the Union) had ratified it by February 3, 1913, and Secretary of State Philander Knox certified it as part of the Constitution on February 25, 1913.6National Archives. 16th Amendment to the US Constitution – Federal Income Tax (1913) Later that same year, Congress enacted a 1 percent tax on net personal income above $3,000, with a surtax that climbed to 6 percent on incomes over $500,000.7Internal Revenue Service. Historical Highlights of the IRS The federal income tax has been continuously in force ever since.
What Income the Amendment Reaches
The phrase “from whatever source derived” is the operative language on scope. It means Congress is not confined to taxing wages. Salaries, hourly pay, tips, business profits, rental income, interest on savings, stock dividends, capital gains from selling property, royalties, and gambling winnings all fall within the federal taxing power granted by the amendment.1Congress.gov. US Constitution – Sixteenth Amendment The breadth is deliberate. By declining to list specific categories, the drafters left room for forms of wealth that didn’t yet exist in 1913, from stock options to cryptocurrency gains.
One recurring question is whether income has to be “realized” (actually received, or converted into cash) before Congress can tax it. In 2024, the Supreme Court touched on this in Moore v. United States but declined to resolve it. The Court upheld a tax on foreign corporate earnings attributed to American shareholders, finding the income had been realized by the corporation even though the shareholders had not received a payout.8Supreme Court of the United States. Moore v United States (06/20/2024) Whether Congress could tax purely unrealized gains, such as the paper appreciation of stock you still hold, remains an open constitutional question.
How the Amendment Enabled Progressive Tax Brackets
The amendment does not require graduated rates. Congress could, in principle, impose a single flat rate on everyone. What the amendment did do is remove the apportionment cage that had made graduated rates constitutionally impossible. Under apportionment, the totals had to come out to each state’s population share, so Congress could not build a system in which higher earners paid higher percentages regardless of where they lived. Once that constraint was gone, Congress gained the flexibility to design marginal brackets, personal exemptions, deductions, and credits. The entire modern federal tax code, including today’s seven-bracket structure that runs from 10 percent to 37 percent, sits on that foundation.9Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026, Including Amendments From the One, Big, Beautiful Bill
The amendment also produced geographic uniformity. Because income taxation no longer had to track state population, Congress could set one national rate schedule. A person earning $80,000 in Mississippi faces the same federal brackets as a person earning $80,000 in New York, something apportionment would have made impossible.
Why “The Income Tax Is Unconstitutional” Arguments Fail
Since 1913, a persistent line of tax protesters has argued that the Sixteenth Amendment was never properly ratified, that filing is voluntary, or that wages aren’t income. Federal courts have rejected every version of these arguments, and have described them as “tax-protester rhetoric that has been universally rejected.”10Internal Revenue Service. The Truth About Frivolous Tax Arguments – Section III The Secretary of State’s 1913 certification is protected by administrative finality, and no court has come close to disturbing it.
The consequences of trying anyway are steep. A return based on a frivolous position triggers a $5,000 civil penalty per submission, and the same $5,000 penalty applies to frivolous requests for hearings, installment agreements, or similar filings.11Office of the Law Revision Counsel. 26 USC 6702 – Frivolous Tax Submissions The IRS can add 20 percent of any underpayment attributable to negligence, or 75 percent for fraud.10Internal Revenue Service. The Truth About Frivolous Tax Arguments – Section III Taking a frivolous case to Tax Court exposes you to an additional penalty of up to $25,000. Willfully attempting to evade federal taxes is a felony under 26 U.S.C. § 7201, carrying up to five years in prison and a fine of up to $100,000 for individuals.12Office of the Law Revision Counsel. 26 USC 7201 – Attempt to Evade or Defeat Tax The Sixteenth Amendment is settled law, and treating it as optional is one of the fastest ways to turn a tax bill into a criminal case.