History.
Constitutional.
Article 1, Section 8, Clause 1 of the United States Constitution (the "Taxing and Spending Clause"), specifies Congress's power to impose "Taxes, Duties, Imposts and Excises", but Article 1, Section 8 requires that, "Duties, Imposts and Excises shall be uniform throughout the United States."
The Constitution specifically stated Congress' method of imposing direct taxes, by requiring Congress to distribute direct taxes in proportion to each state's population "determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons". It has been argued that head taxes and property taxes (slaves could be taxed as either or both) were likely to be abused, and that they bore no relation to the activities in which the federal government had a legitimate interest. The fourth clause of section 9 therefore specifies that, "No Capitation, or other direct, Tax shall be laid, unless in Proportion to the Census or enumeration herein before directed to be taken."
Taxation was also the subject of Federalist No. 33 penned secretly by the Federalist Alexander Hamilton under the pseudonym Publius. In it, he asserts that the wording of the "Necessary and Proper" clause should serve as guidelines for the legislation of laws regarding taxation. The legislative branch is to be the judge, but any abuse of those powers of judging can be overturned by the people, whether as states or as a larger group.
The courts have generally held that direct taxes are limited to taxes on people (variously called "capitation", "poll tax" or "head tax") and property. All other taxes are commonly referred to as "indirect taxes," because they tax an event, rather than a person or property per se. What seemed to be a straightforward limitation on the power of the legislature based on the subject of the tax proved inexact and unclear when applied to an income tax, which can be arguably viewed either as a direct or an indirect tax.
Early federal income taxes.
The first income tax suggested in the United States was during the War of 1812. The idea for the tax was based on the British Tax Act of 1798. The British tax law applied progressive rates to income. The British tax rates ranged from 0.833% on income starting at £60 to 10% on income above £200. The tax proposal was developed in 1814. Because the treaty of Ghent was signed in 1815, ending hostilities and the need for additional revenue, the tax was never imposed in the United States.
In order to help pay for its war effort in the American Civil War, Congress imposed the first federal income tax in U.S. history through passage of the Revenue Act of 1861. The act created a flat tax of three percent on incomes above $800 ($23,000 in current dollar terms). This taxation of income reflected the increasing amount of wealth held in stocks and bonds rather than property, which the federal government had taxed in the past. The Revenue Act of 1862 established the first national inheritance tax and added a progressive taxation structure to the federal income tax, implementing a tax of five percent on incomes above $10,000. Congress later further raised taxes, and by the end of the war, the income tax constituted about one-fifth of the revenue of the federal government. To collect these taxes, Congress created the Office of the Commissioner of Internal Revenue within the Treasury Department. The federal income tax would remain in effect until its repeal in 1872.
