A federal wealth tax is very likely unconstitutional under current Supreme Court doctrine, and the reason is a single clause the Framers wrote into Article I. The Constitution treats taxes on property as “direct taxes” that must be apportioned among the states by population, and apportioning a tax on net worth produces effective rates so uneven across states that no such tax has ever been enacted. Whether that barrier holds depends on how the Court eventually classifies a wealth tax, and as of the Court’s 2024 decision in Moore v. United States, it has deliberately declined to answer.
The Apportionment Rule Is the Core Problem
Article I, Section 9 says “No Capitation, or other direct, Tax shall be laid, unless in Proportion to the Census.”1Cornell Law School. U.S. Constitution Annotated – Article I, Section 9, Clause 4 In practice that means the total revenue collected from each state has to match that state’s share of the national population, not its share of the national wealth.
Run the numbers and the problem becomes obvious. If Congress wants to raise $100 billion from a wealth tax, a state with 3% of the population owes $3 billion regardless of whether its residents hold 3% or half a percent of the country’s taxable wealth. Residents of states packed with billionaires end up paying modest effective rates. Residents of lower-wealth states pay dramatically higher rates on identical assets. Two people with the same net worth living in different states would owe wildly different amounts. That geographic randomness is why the apportionment rule functions as a practical prohibition rather than a mere procedural hurdle. No Congress is going to pass a tax that works that way.
Article I, Section 8 gives Congress broad authority to “lay and collect Taxes, Duties, Imposts and Excises,” subject only to the requirement that indirect taxes be “uniform throughout the United States.”2LII / Legal Information Institute. Historical Background of the Taxing Power Uniformity is a low bar: same rate, same terms, everywhere. The entire constitutional question about a wealth tax is which bucket it falls into.
How Courts Have Defined “Direct” Taxes
The Framers never spelled out what counts as a direct tax, so the answer has come from the Supreme Court, and it has shifted over time.
In Hylton v. United States (1796), the Court upheld an unapportioned federal tax on carriages and suggested that only two kinds of taxes were clearly direct: head taxes and taxes on land.3Justia U.S. Supreme Court Center. Hylton v. United States, 3 U.S. 171 (1796) Under that narrow reading, a wealth tax on financial assets might have been permissible.
A century later the Court reversed course. In Pollock v. Farmers’ Loan and Trust Co. (1895), it struck down an unapportioned federal income tax, holding that “taxes on real estate being indisputably direct taxes, taxes on the rents or income of real estate are equally direct taxes,” and extending the same logic to personal property and the income from it.4Justia U.S. Supreme Court Center. Pollock v. Farmers’ Loan and Trust Company, 158 U.S. 601 (1895) Pollock is the precedent wealth tax opponents lean on hardest. If taxing the income from property is a direct tax, taxing the property itself is even more obviously direct.
Does the Sixteenth Amendment Save a Wealth Tax?
The Sixteenth Amendment was ratified in 1913 specifically to overturn Pollock. It gives Congress 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.”5Legal Information Institute at Cornell Law School. 16th Amendment It carved out one exception to the apportionment rule: income. Everything turns on whether a wealth tax fits that word.
Supporters read the amendment broadly. Income “from whatever source derived” is capacious language, and a tax on annual increases in net worth is, in their view, functionally a tax on economic gains during the year. Under that reading, taxing unrealized appreciation qualifies as taxing income.
Opponents rely on Eisner v. Macomber (1920), where the Court defined income as “a gain, a profit, something of exchangeable value, proceeding from the property, severed from the capital” and added that “mere growth or increment of value in a capital investment is not income.”6Justia U.S. Supreme Court Center. Eisner v. Macomber, 252 U.S. 189 (1920) That is the origin of the realization requirement. A stock portfolio worth more on December 31 than it was on January 1 has not produced anything “severed from the capital,” so under Eisner, the appreciation is not income. If unrealized gains are not income, the Sixteenth Amendment offers no shelter, and the tax falls back into apportionment.
What Moore v. United States Signals
The Supreme Court had a chance to resolve the realization question in 2024 and passed on it. Moore v. United States involved the Mandatory Repatriation Tax, which taxed American shareholders on the accumulated earnings of foreign corporations they partly owned even though those earnings had never been distributed. The Court upheld the tax on narrow grounds: Congress may attribute the “realized and undistributed income” of a foreign corporation to its American shareholders, based on a long history of pass-through taxation for partnerships and similar entities.7Supreme Court of the United States. Moore v. United States (2024) The corporation had already realized the income; the only question was attribution.
On realization itself, the majority wrote: “To decide this case, we need not resolve that disagreement over realization. Those are potential issues for another day.”7Supreme Court of the United States. Moore v. United States (2024) The government even conceded that “a hypothetical unapportioned tax on an individual’s holdings or wealth might be considered a tax on property, not income.”
The separate opinions matter for anyone trying to read the Court. Justice Barrett, joined by Justice Alito, wrote that the Sixteenth Amendment’s reference to income “derived” from a source “encompasses a requirement that income, to be taxed without apportionment, must be realized.” Justice Thomas, joined by Justice Gorsuch, was blunter: “Sixteenth Amendment ‘incomes’ include only income realized by the taxpayer.” Justice Jackson took the other side, writing that the “alleged requirement appears nowhere in the text of the Sixteenth Amendment.”7Supreme Court of the United States. Moore v. United States (2024)
So the count is roughly this: four justices have signaled that realization is constitutionally required, one has said it is not, and five have not committed. A wealth tax that reaches unrealized appreciation would force the Court to answer, and a proponent would need to persuade at least one of the uncommitted five that yearly gains in asset value qualify as income under the Sixteenth Amendment.
Congress Already Taxes Some Unrealized Gains
The strongest counter to the realization-is-required position is that Congress has been taxing unrealized gains for decades in specific contexts, and those provisions have never been struck down.
Section 1256 of the Internal Revenue Code treats certain futures and options positions “as sold for its fair market value on the last business day of such taxable year,” forcing holders to recognize gain or loss without any actual sale.8Office of the Law Revision Counsel. 26 U.S. Code 1256 – Section 1256 Contracts Marked to Market Similar mark-to-market treatment is available to shareholders of certain foreign investment funds under Section 1296.9Internal Revenue Service. Instructions for Form 8621 (12/2025)
The most aggressive example is the expatriation tax. Under Section 877A, when a wealthy American renounces citizenship, all of their property is “treated as sold on the day before the expatriation date for its fair market value,” triggering tax on paper gains.10Office of the Law Revision Counsel. 26 USC 877A – Tax Responsibilities of Expatriation It applies to individuals whose average annual income tax liability exceeded $206,000 over the prior five years or whose net worth is at least $2 million.11Internal Revenue Service. Expatriation Tax
How much these provisions prove is debatable. Futures contracts settle daily through a clearinghouse, so mark-to-market tracks real economic settlement rather than a legal fiction. The expatriation tax is triggered by a specific event (renouncing citizenship), not levied annually on ownership. A recurring yearly tax on the full asset base of high-net-worth individuals is a broader animal than any of these targeted rules, and whether the Court would extend the precedents that far is exactly what Moore left unresolved.
Fifth Amendment Problems Even If Apportionment Is Cleared
Suppose the Court finds a way around the direct tax problem. A wealth tax would still face challenges under the Fifth Amendment.
Valuation and Due Process
The Due Process Clause bars the government from depriving anyone of property “without due process of law.”12Cornell Law School. Fifth Amendment Publicly traded stock is easy to value. Private businesses, real estate, art, and partnership interests are not. Two qualified appraisers can look at the same private company and produce valuations that differ by tens of millions of dollars.
The stakes are real. A $200 million disagreement over the value of a private company, at a 2% wealth tax rate, is $4 million in tax per year. Consistent, defensible valuation across taxpayers becomes a constitutional issue, not just an administrative one. The Ultra-Millionaire Tax Act of 2026, currently pending in Congress, tries to force accurate reporting by imposing a 30% penalty when reported value is 65% or less of the correct amount, escalating to 50% for gross misstatements below 40% of correct value.13U.S. Congress. H.R. 8085 – Ultra-Millionaire Tax Act of 2026 Steep penalties for misvaluation only sharpen the due process concern when the “correct” value is itself contested.
The Takings Argument
The Fifth Amendment also requires “just compensation” when property is taken for public use.14Legal Information Institute. Takings Clause – Overview A tax is not usually a taking, and the bar is high. But the argument gains some weight at extreme rates. A 5% annual tax compounding over a decade can consume a substantial share of an asset that grows slowly or not at all. Modest wealth tax proposals would probably survive a takings challenge; very aggressive ones might not, which puts a practical ceiling on how high rates can go.
Where the Legislation Stands
No federal wealth tax has ever been enacted, and the constitutional questions have never been directly litigated. Proposals keep coming anyway.
H.R. 8085, the Ultra-Millionaire Tax Act of 2026, was introduced in March 2026. It would impose a 2% annual tax on net assets above $50 million and a 3% tax on net assets above $1 billion, rising to 6% above $1 billion if certain conditions are met.13U.S. Congress. H.R. 8085 – Ultra-Millionaire Tax Act of 2026
A separate proposal, the Billionaire Minimum Income Tax, tries a different route. It would impose a 25% minimum tax on individuals with net worth exceeding $100 million, calculated on their total income including unrealized capital gains. By framing the base as “income,” proponents hope to fit within the Sixteenth Amendment. Whether the Court would accept that framing is the whole question. Calling unrealized appreciation “income” in the statute does not automatically make it income for constitutional purposes, and any such law would draw an immediate legal challenge.
One boundary worth flagging: the apportionment rule is a federal constraint only. State wealth taxes face their own constitutional questions under state constitutions and the federal Due Process and Commerce Clauses, but not the direct tax rule. So the analysis in this article applies to a federal wealth tax; a state proposal is a different constitutional argument.
Given the current Court, the honest answer for a federal wealth tax on net worth is that it would almost certainly be struck down as an unapportioned direct tax unless it is carefully engineered to look like an income tax on realized gains, and even then at least four justices appear prepared to say that unrealized appreciation is not income at all.