Sixteenth Amendment to the United States Constitution
|United States of America|
This article is part of the series:
|Original text of the Constitution|
|Amendments to the Constitution|
|Full text of the Constitution|
Other countries · Law Portal
The Sixteenth Amendment (Amendment XVI) to the United States Constitution allows the Congress to levy an income tax without apportioning it among the states or basing it on Census results. This amendment exempted income taxes from the constitutional requirements regarding direct taxes, after income taxes on rents, dividends, and interest were ruled to be direct taxes in Pollock v. Farmers' Loan & Trust Co. (1895). It was ratified on February 3, 1913.
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.
Other Constitutional provisions regarding taxes 
Article I, Section 2, Clause 3:
Article I, Section 8, Clause 1:
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.
Article I, Section 9, Clause 4:
No Capitation, or other direct, Tax shall be laid, unless in proportion to the Census or Enumeration herein before directed to be taken.
This clause basically refers to a tax on property, such as a tax based on the value of land, as well as a capitation.
Income taxes pre-Pollock 
Until 1913, customs duties (tariffs) and excise taxes were the primary sources of federal revenue. During the War of 1812, Secretary of the Treasury A.J. Dallas made the first public proposal for an income tax, but it was never implemented. The Congress did introduce an income tax to fund the Civil War through the Revenue Act of 1861. It levied a flat tax of 3% on annual income above $800, which was equivalent to $20,441 in today's money. This act was replaced the following year with the Revenue Act of 1862, which levied a graduated tax of 3–5% on income above $600 (worth $13,798 today) and specified a termination of income taxation in 1866. The Civil War income taxes, which expired in 1872, proved to be both highly lucrative and highly skewed against the more industrialized states, with New York, Pennsylvania and Massachusetts generating about 60 percent of the total revenue collected. In the two decades following the expiration of the Civil War income tax, the Greenback movement, the Labor Reform Party, the Populist Party, the Democratic Party and many others would call for a graduated income tax.
The Socialist Labor Party advocated a graduated income tax in 1887. The Populist Party "demand[ed] a graduated income tax" in its 1892 platform. The Democratic Party, led by William Jennings Bryan, advocated the income tax law passed in 1894, and proposed an income tax in its 1908 platform.
Prior to the Supreme Court's decision in Pollock v. Farmers' Loan & Trust Co., all income taxes had been considered indirect taxes imposed without respect to geography, unlike direct taxes, that must be apportioned among the states according to population.
The Pollock case 
In 1894, an amendment was attached to the Wilson–Gorman Tariff Act that attempted to impose a federal tax of 2% on incomes over $4,000 (worth $106,138 today). The income tax law was strongly favored in the South and moderately supported in the eastern North Central states but heavily opposed in the West and the Northeast (with the exception of New Jersey). Derided as "un-Democratic, inquisitorial, and wrong in principle," it was challenged in federal court.
In Pollock v. Farmers' Loan & Trust Co., the Supreme Court declared certain taxes on incomes — such as those on property under the 1894 Act — to be unconstitutionally unapportioned direct taxes. The Court reasoned that a tax on income from property should be treated as a tax on "property by reason of its ownership" and so should be required to be apportioned. The reasoning was that taxes on the rents from land, the dividends from stocks and so forth burdened the property generating the income in the same way that a tax on "property by reason of its ownership" burdened that property.
After Pollock, while income taxes on wages (as indirect taxes) were still not required to be apportioned by population, taxes on interest, dividends and rent income were required to be apportioned by population. The Pollock ruling made the source of the income (e.g., property versus labor, etc.) relevant in determining whether the tax imposed on that income was deemed to be "direct" (and thus required to be apportioned among the states according to population) or, alternatively, "indirect" (and thus required only to be imposed with geographical uniformity).
In his dissent to the Pollock decision, Justice John Marshall Harlan stated:
When, therefore, this court adjudges, as it does now adjudge, that Congress cannot impose a duty or tax upon personal property, or upon income arising either from rents of real estate or from personal property, including invested personal property, bonds, stocks, and investments of all kinds, except by apportioning the sum to be so raised among the States according to population, it practically decides that, without an amendment of the Constitution — two-thirds of both Houses of Congress and three-fourths of the States concurring — such property and incomes can never be made to contribute to the support of the national government.
Members of Congress responded to Pollock by expressing widespread concern that many of the wealthiest Americans had consolidated too much economic power.
On June 16, 1909, President William Howard Taft, in an address to Congress, proposed a 2% federal income tax on corporations by way of an excise tax and a constitutional amendment to allow the previously enacted income tax.
An income tax amendment to the Constitution was first proposed by Senator Norris Brown of Nebraska. He submitted two proposals, Senate Resolutions Nos. 25 and 39. The amendment proposal finally accepted was Senate Joint Resolution No. 40, introduced by Senator Nelson W. Aldrich of Rhode Island, the Senate majority leader and Finance Committee Chairman.
On July 12, 1909, the resolution proposing the Sixteenth Amendment was passed by the Sixty-first Congress and was submitted to the state legislatures. Support for the income tax was strongest in the western and southern states and opposition was strongest in the northeastern states. Supporters of the income tax believed that it would be a much better method of gathering revenue than tariffs, which were the primary source of revenue at the time. From well before 1894, Democrats, Progressives, Populists and other left-oriented parties argued that tariffs disproportionately affected the poor, interfered with prices, were unpredictable, and were an intrinsically limited source of revenue. The South and the West tended to support income taxes because their residents were generally less prosperous, more agricultural and more sensitive to fluctuations in commodity prices. A sharp rise in the cost of living between 1897 and 1913 greatly increased support for the idea of income taxes, including in the urban Northeast. A growing number of Republicans also began supporting the idea, notably Theodore Roosevelt and the "Insurgent" Republicans (who would go on to form the Progressive Party). These Republicans were driven mainly by a fear of the increasingly large and sophisticated military forces of Japan, Britain and the European powers, their own imperial ambitions and the perceived need to defend American merchant ships. Moreover, these progressive Republicans were, as the name suggests, convinced that central governments could play a positive role in national economies. A bigger government and a bigger military, of course, required a correspondingly larger and steadier source of revenue to support it.
Opposition to the Sixteenth Amendment was led by establishment Republicans because of their close ties to wealthy industrialists, although not even they were uniformly opposed to the general idea of a permanent income tax. In 1910, New York Governor Charles Evans Hughes, shortly before becoming a Supreme Court Justice, spoke out against the income tax amendment. While he supported the idea of a federal income tax, Hughes believed the words "from whatever source derived" in the proposed amendment implied that the federal government would have the power to tax state and municipal bonds. He believed this would excessively centralize governmental power and "would make it impossible for the state to keep any property".
Between 1909 and 1913, several conditions favored passage of the Sixteenth Amendment. Inflation was high and many blamed Federal tariffs for the rising prices. The Republican Party was divided and weakened by the loss of Roosevelt and the Insurgents who joined the Progressive party, a problem that blunted opposition even in the Northeast. The Democrats won both houses and the Presidency in 1912 and the country was generally in a left-leaning mood, with the Socialist Party winning a seat in the House in 1910 and polling six percent of the popular presidential vote in 1912.
Three advocates for a federal income tax ran in the presidential election of 1912. On February 25, 1913, Secretary of State Philander Knox proclaimed that the amendment had been ratified by three-fourths of the states and so had become part of the Constitution. The Revenue Act of 1913 was enacted shortly thereafter.
- Alabama (August 10, 1909)
- Kentucky (February 8, 1910)
- South Carolina (February 19, 1910)
- Illinois (March 1, 1910)
- Mississippi (March 7, 1910)
- Oklahoma (March 10, 1910)
- Maryland (April 8, 1910)
- Georgia (August 3, 1910)
- Texas (August 16, 1910)
- Ohio (January 19, 1911)
- Idaho (January 20, 1911)
- Oregon (January 23, 1911)
- Washington (January 26, 1911)
- Montana (January 27, 1911)
- Indiana (January 30, 1911)
- California (January 31, 1911)
- Nevada (January 31, 1911)
- South Dakota (February 1, 1911)
- Nebraska (February 9, 1911)
- North Carolina (February 11, 1911)
- Colorado (February 15, 1911)
- North Dakota (February 17, 1911)
- Michigan (February 23, 1911)
- Iowa (February 24, 1911)
- Kansas (March 2, 1911)
- Missouri (March 16, 1911)
- Maine (March 31, 1911)
- Tennessee (April 7, 1911)
- Arkansas (April 22, 1911), after having previously rejected the amendment
- Wisconsin (May 16, 1911)
- New York (July 12, 1911)
- Arizona (April 3, 1912)
- Minnesota (June 11, 1912)
- Louisiana (June 28, 1912)
- West Virginia (January 31, 1913)
- Delaware (February 3, 1913)
Ratification (by the requisite 36 states) was completed on February 3, 1913 with the ratification by Delaware. The amendment was subsequently ratified by the following states, bringing the total number of ratifying states to forty-two of the forty-eight then existing:
- 37. New Mexico (February 3, 1913)
- 38. Wyoming (February 3, 1913)
- 39. New Jersey (February 4, 1913)
- 40. Vermont (February 19, 1913)
- 41. Massachusetts (March 4, 1913)
- 42. New Hampshire (March 7, 1913), after rejecting the amendment on March 2, 1911
The legislatures of the following states rejected the amendment without ever subsequently ratifying it:
The legislatures of the following states never considered the proposed amendment:
Pollock overruled 
The Sixteenth Amendment overruled the Pollock decision. That means the Congress may impose taxes on income from any source without having to apportion the total dollar amount of tax collected from each state according to each state's population in relation to the total national population.
In Wikoff v. Commissioner, the United States Tax Court said:
[I]t is immaterial, with respect to Federal income taxes, whether the tax is a direct or an indirect tax. Mr. Wikoff [the taxpayer] relied on the Supreme Court's decision in Pollock v. Farmers' Loan & Trust Co. [ . . . ] but the effect of that decision has been nullified by the enactment of the 16th Amendment.
In Abrams v. Commissioner, the Tax Court said:
Since the ratification of the Sixteenth Amendment, it is immaterial with respect to income taxes, whether the tax is a direct or indirect tax. The whole purpose of the Sixteenth Amendment was to relieve all income taxes when imposed from [the requirement of] apportionment and from [the requirement of] a consideration of the source whence the income was derived.
Case law 
The federal courts' interpretations of the Sixteenth Amendment have changed considerably over time and there have been many disputes about the applicability of the amendment.
The Brushaber case 
In Brushaber v. Union Pacific Railroad, 240 U.S. 1 (1916), the Supreme Court ruled that (1) the Sixteenth Amendment removes the Pollock requirement that certain income taxes (such as taxes on income "derived from real property" that were the subject of the Pollock decision), be apportioned among the states according to population; (2) the federal income tax statute does not violate the Fifth Amendment's prohibition against the government taking property without due process of law; (3) the federal income tax statute does not violate the Article I, Section 8, Clause 1 requirement that excises, also known as indirect taxes, be imposed with geographical uniformity.
The Kerbaugh-Empire Co. case 
It was not the purpose or the effect of that amendment to bring any new subject within the taxing power. Congress already had the power to tax all incomes. But taxes on incomes from some sources had been held to be "direct taxes" within the meaning of the constitutional requirement as to apportionment. [cites omitted] The Amendment relieved from that requirement and obliterated the distinction in that respect between taxes on income that are direct taxes and those that are not, and so put on the same basis all incomes "from whatever source derived". [cites omitted] "Income" has been taken to mean the same thing as used in the Corporation Excise Tax of 1909 (36 Stat. 112), in the Sixteenth Amendment, and in the various revenue acts subsequently passed. [cites omitted] After full consideration, this court declared that income may be defined as gain derived from capital, from labor, or from both combined, including profit gained through sale or conversion of capital.
The Glenshaw Glass case 
In Commissioner v. Glenshaw Glass Co., 348 U.S. 426 (1955), the Supreme Court laid out what has become the modern understanding of what constitutes 'gross income' to which the Sixteenth Amendment applies, declaring that income taxes could be levied on "accessions to wealth, clearly realized, and over which the taxpayers have complete dominion." Under this definition, any increase in wealth — whether through wages, benefits, bonuses, sale of stock or other property at a profit, bets won, lucky finds, awards of punitive damages in a lawsuit, qui tam actions — are all within the definition of income, unless the Congress makes a specific exemption, as it has for items such as life insurance proceeds received by reason of the death of the insured party, gifts, bequests, devises and inheritances, and certain scholarships.
Income taxation of wages, etc. 
Federal courts have ruled that the Sixteenth Amendment allows a direct tax on "wages, salaries, commissions, etc. without apportionment."
The Penn Mutual case 
Although the Sixteenth Amendment is often cited as the "source" of the Congressional power to tax incomes, at least one court has reiterated the point made in Brushaber and other cases that the Sixteenth Amendment itself did not grant the Congress the power to tax incomes, a power the Congress had since 1789, but only removed the possible requirement that any income tax be apportioned among the states according to their respective populations. In Penn Mutual Indemnity, the United States Tax Court stated:
In dealing with the scope of the taxing power the question has sometimes been framed in terms of whether something can be taxed as income under the Sixteenth Amendment. This is an inaccurate formulation... and has led to much loose thinking on the subject. The source of the taxing power is not the Sixteenth Amendment; it is Article I, Section 8, of the Constitution.
The United States Court of Appeals for the Third Circuit agreed with the Tax Court, stating:
It did not take a constitutional amendment to entitle the United States to impose an income tax. Pollock v. Farmers' Loan & Trust Co., 157 U. S. 429, 158 U. S. 601 (1895), only held that a tax on the income derived from real or personal property was so close to a tax on that property that it could not be imposed without apportionment. The Sixteenth Amendment removed that barrier. Indeed, the requirement for apportionment is pretty strictly limited to taxes on real and personal property and capitation taxes.
It is not necessary to uphold the validity of the tax imposed by the United States that the tax itself bear an accurate label. Indeed, the tax upon the distillation of spirits, imposed very early by federal authority, now reads and has read in terms of a tax upon the spirits themselves, yet the validity of this imposition has been upheld for a very great many years.
It could well be argued that the tax involved here [an income tax] is an "excise tax" based upon the receipt of money by the taxpayer. It certainly is not a tax on property and it certainly is not a capitation tax; therefore, it need not be apportioned. We do not think it profitable, however, to make the label as precise as that required under the Food and Drug Act. Congress has the power to impose taxes generally, and if the particular imposition does not run afoul of any constitutional restrictions then the tax is lawful, call it what you will.
The Murphy case 
On December 22, 2006, a three-judge panel of the United States Court of Appeals for the District of Columbia Circuit vacated its unanimous August 2006 opinion in Murphy v. Internal Revenue Service and United States. In an unrelated matter, the court had also granted the government's motion to dismiss Murphy's suit against the "Internal Revenue Service." Under federal sovereign immunity, a taxpayer may sue the federal government, but not a government agency, officer, or employee (with few exceptions). The court stated:
Insofar as the Congress has waived sovereign immunity with respect to suits for tax refunds under eo nomine in this case., that provision specifically contemplates only actions against the "United States." Therefore, we hold the IRS, unlike the United States, may not be sued
An exception to federal sovereign immunity is in the United States Tax Court, where a taxpayer may sue the Commissioner of Internal Revenue. The original three-judge panel then agreed to rehear the case itself. In its original decision, the Court had ruled that was unconstitutional under the Sixteenth Amendment to the extent that the statute purported to tax, as income, a recovery for a non-physical personal injury for mental distress and loss of reputation not received in lieu of taxable income such as lost wages or earnings.
Because the August 2006 opinion was vacated, the full court did not hear the case en banc.
On July 3, 2007, the Court (through the original three-judge panel) ruled (1) that the taxpayer's compensation was received on account of a non-physical injury or sickness; (2) that gross income under section 61 of the Internal Revenue Code does include compensatory damages for non-physical injuries, even if the award is not an "accession to wealth," (3) that the income tax imposed on an award for non-physical injuries is an indirect tax, regardless of whether the recovery is restoration of "human capital," and therefore the tax does not violate the constitutional requirement of Article I, Section 9, Clause 4, that capitations or other direct taxes must be laid among the states only in proportion to the population; (4) that the income tax imposed on an award for non-physical injuries does not violate the constitutional requirement of Article I, Section 8, Clause 1, that all duties, imposts and excises be uniform throughout the United States; (5) that under the doctrine of sovereign immunity, the Internal Revenue Service may not be sued in its own name.
The Court stated that "[a]lthough the 'Congress cannot make a thing income which is not so in fact,' [ . . . ] it can label a thing income and tax it, so long as it acts within its constitutional authority, which includes not only the Sixteenth Amendment but also Article I, Sections 8 and 9." The court ruled that Ms. Murphy was not entitled to the tax refund she claimed, and that the personal injury award she received was "within the reach of the congressional power to tax under Article I, Section 8 of the Constitution"—even if the award was "not income within the meaning of the Sixteenth Amendment". See also the Penn Mutual case cited above.
On April 21, 2008, the Supreme Court declined to review the Court of Appeals decision.
See also 
- Knowlton v. Moore 178 U.S. 41 (1900) and Flint v. Stone Tracy Co. 220 U.S. 107 (1911)
- Hylton v. United States 3 U.S. 171 (1796)
- Buenker, John D. 1981. "The Ratification of the Sixteenth Amendment." The Cato Journal. 1:1. PDF
- Baack, Bennet T. and Edward John Ray. 1985. "Special Interests and the Adoption of the Income Tax in the United States." The Journal of Economic History V. 45, No. 3. pp. 607-625.
- "On This Day: Congress Passes Act Creating First Income Tax". Findingdulcinea.com. Retrieved 2012-03-26.
- Staff. Consumer Price Index (estimate) 1800–2012. Federal Reserve Bank of Minneapolis. Retrieved March 31, 2013.
- Baack and Ray, p. 608.
- "Socialist Labor Party Platform" (PDF). Retrieved 2012-03-26.
- "Populist Party Platform, 1892". Historymatters.gmu.edu. Retrieved 2012-03-26.
- Speeches of William Jennings Bryan, pp. 159-179. Books.google.com. Retrieved 2012-03-26.
- 1908 Democratic party platform[dead link]
- Commentary, James W. Ely, Jr., on the case of Springer v. United States, in answers.com, at 
- "Again the situation is aptly illustrated by the various acts taxing incomes derived from property of every kind and nature which were enacted beginning in 1861, and lasting during what may be termed the Civil War period. It is not disputable that these latter taxing laws were classed under the head of excises, duties, and imposts because it was assumed that they were of that character inasmuch as, although putting a tax burden on income of every kind, including that derived from property real or personal, they were not taxes directly on property because of its ownership.” Brushaber v. Union Pac. Railroad, 240 U.S. 1 (1916), at 15
- Baack and Ray, p. 610
- "Mr. Cockran's Final Effort" (PDF). New York Times. 1894-01-31.
- Read a description of the decision at the Tax History Museum
- "Justice Harlan's dissenting opinion in ''Pollock''". Law.cornell.edu. Retrieved 2012-03-26.
- See the quotes from Theodore Roosevelt at the Tax History Museum
- "Taft Address of June 16, 1909 (American Presidency Project)". Presidency.ucsb.edu. 1909-06-16. Retrieved 2012-03-26.
- President Taft Presidential addresses. Books.google.com. Retrieved 2012-03-26.
- Volume 36, Statutes at Large, 61st Congress Session I, Senate Joint Resolution No. 40, p. 184, approved July 31, 1909
- Senate Joint Resolution 40, 36 Stat. 184.
- "The Ratification of the Federal Income Tax Amendment, John D. Buenker" (PDF). Retrieved 2012-03-26.
- Buenker, p. 186.
- Buenker, p. 189
- Baack and Jay, p. 613-614
- Buenker, p. 184
- "Arthur A. Ekirch, Jr., "The Sixteenth Amendment: The Historical Background," p. 175, ''Cato Journal'', Vol. 1, No. 1, Spring 1981." (PDF). Retrieved 2012-03-26.
- Buenker, pp. 219-221
- Adam Young, "The Origin of the Income Tax", Ludwig von Mises Institute, Sept. 7, 2004
- "FindLaw: U.S. Constitution: Amendments". FindLaw. Retrieved 2012-03-26.
- "Ratification of Constitutional Amendments". U.S. Constitution Online. Retrieved April 20, 2012.
- "Virginia House Opposes Federal Clause by 54 to 37", The Washington Post, March 8, 1910
- Boris Bittker, "Constitutional Limits on the Taxing Power of the Federal Government," The Tax Lawyer, Fall 1987, Vol. 41, No. 1, p. 3 (American Bar Association) (Pollock case "was in effect reversed by the sixteenth amendment")
- "The Sixteenth Amendment to the Constitution overruled Pollock [ . . . ]" Graf v. Commissioner, 44 T.C.M. (CCH) 66, TC Memo. 1982-317, CCH Dec. 39,080(M) (1982).
- William D. Andrews, Basic Federal Income Taxation, p. 2, Little, Brown and Company (3d ed. 1985) ("In 1913 the Sixteenth Amendment to the Constitution was adopted, overruling Pollock.").
- "Findlaw: Sixteenth Amendment, History and Purpose of the Amendment". Caselaw.lp.findlaw.com. Retrieved 2012-03-26.
- Wikoff v. Commissioner, 37 T.C.M. (CCH) 1539, T.C. Memo. 1978-372 (1978).
- 82 T.C. 403, CCH Dec. 41,031 (1984)
- "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 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." Boris I. Bittker, Martin J. McMahon, Jr. & Lawrence A. Zelenak, Federal Income Taxation of Individuals, ch. 1, paragr. 1.01[a], Research Institute of America (2d ed. 2005), as retrieved from 2002 WL 1454829 (W. G. & L.).
- 26 U.S.C. § 101.
- 26 U.S.C. § 102.
- 26 U.S.C. § 117.
- Parker v. Commissioner, 724 F.2d 469, 84-1 U.S. Tax Cas. (CCH) paragr. 9209 (5th Cir. 1984) (closing parenthesis in original has been omitted). For other court decisions upholding the taxability of wages, salaries, etc. see United States v. Connor, 898 F.2d 942, 90-1 U.S. Tax Cas. (CCH) paragr. 50,166 (3d Cir. 1990); Perkins v. Commissioner, 746 F.2d 1187, 84-2 U.S. Tax Cas. (CCH) paragr. 9898 (6th Cir. 1984); White v. United States, 2005-1 U.S. Tax Cas. (CCH) paragr. 50,289 (6th Cir. 2004), cert. denied, ____ U.S. ____ (2005); Granzow v. Commissioner, 739 F.2d 265, 84-2 U.S. Tax Cas. (CCH) paragr. 9660 (7th Cir. 1984); Waters v. Commissioner, 764 F.2d 1389, 85-2 U.S. Tax Cas. (CCH) paragr. 9512 (11th Cir. 1985); United States v. Buras, 633 F.2d 1356, 81-1 U.S. Tax Cas. (CCH) paragr. 9126 (9th Cir. 1980).
- Penn Mutual Indemnity Co. v. Commissioner, 32 T.C. 653 at 659 (1959), aff'd, 277 F.2d 16, 60-1 U.S. Tax Cas. (CCH) paragr. 9389 (3d Cir. 1960).
- Penn Mutual Indemnity Co. v. Commissioner, 277 F.2d 16, 60-1 U.S. Tax Cas. (CCH) paragr. 9389 (3d Cir. 1960) (footnotes omitted).
- Order, Dec. 22, 2006, Murphy v. Internal Revenue Service and United States, United States Court of Appeals for the District of Columbia Circuit.
- 460 F.3d 79, 2006-2 U.S. Tax Cas. (CCH) paragr. 50,476, 2006 WL 2411372 (D.C. Cir. August 22, 2006).
- (Murphy v. United States)
- 26 U.S.C. § 61 (Murphy v United States, on rehearing)
- Opinion on rehearing, July 3, 2007, Murphy v. Internal Revenue Service and United States, case no. 05-5139, United States Court of Appeals for the District of Columbia Circuit, 2007-2 U.S. Tax Cas. (CCH) paragr. 50,531 (D.C. Cir. 2007)
- Opinion on rehearing, July 3, 2007, p. 16, Murphy v. Internal Revenue Service and United States, case no. 05-5139, United States Court of Appeals for the District of Columbia Circuit, 2007-2 U.S. Tax Cas. (CCH) paragr. 50,531 (D.C. Cir. 2007).
- Opinion on rehearing, July 3, 2007, p. 5-6, Murphy v. Internal Revenue Service and United States, case no. 05-5139, United States Court of Appeals for the District of Columbia Circuit, 2007-2 U.S. Tax Cas. (CCH) paragr. 50,531 (D.C. Cir. 2007).
- Denniston, Lyle (April 21, 2008). "Court to hear anti-dumping, sentencing cases". SCOTUSblog. Retrieved 21 April 2008.
- National Archives: Sixteenth Amendment
- Sixteenth Amendment and 1913 tax return form Images of original documents
- CRS Annotated Constitution: Sixteenth Amendment
- Pollock Decision The decision nullified by the Sixteenth Amendment
- Brushaber Decision Supreme Court opinion on the apportionment clause of the Constitution.
- Stanton Decision - no new power of taxation (affirming constitutionality of income tax after Sixteenth Amendment)
- History of the U.S. Tax System - Almanac of Policy Issues; annotated as "US Department of the Treasury Undated.".