U.S. Internal Revenue Service Definition
The Internal Revenue Service (IRS) is the United States government agency that collects taxes and enforces the tax laws. It is a part of the Department of the Treasury.
For its first 138 years (1776-1913), the United States did not have a standing federal income tax. Most government revenue was collected from excise taxes on products, import/export taxes, and revenue taxes on items such as photographs, bank checks, stock certificates, wills, deeds, and other legal documents. Several short-term income taxes were levied in the late 19th Century, some of which were declared unconstitutional by the Supreme Court. In 1913 the Sixteenth Amendment to the Constitution removed restrictions on income tax revenue, clearing the way for the income tax to become a permanent institution. The agency created to enforce these taxes was named the internal revenue service in contrast to U.S. government institutions that collected external revenue through duties and tariffs.