The Internal Revenue Service (IRS) is the tax administrator and collector of the United States of America. It’s a bureau of the Department of the Treasury.
In July of 1862, Congress established the Office of the Commissioner of Internal Revenue under the Department of the Treasury. At that time, the Commissioner of the Internal Revenue collected taxes on alcohol, property, and other matters related to internal revenue. In February of 1913, the Sixteenth Amendment of the U.S. Constitution passed, empowering the Congress 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.” The Bureau of Internal Revenue then established the Personal Income division. In 1952, the Bureau of Internal Revenue officially became the Internal Revenue Service. In 2000, under the IRS restructuring and Reform Act, the IRS reorganized itself and created four major business division. (see here for more histories of IRS.)
The Internal Revenue Code (IRC) is the current law governing the acts of IRS. It is under the Title 26 of the United States Code. Violate the IRC can be a crime or a civil offense. For example, to willfully evade tax can cause penalties including fine and imprisonment. (see Chapter 75 of 26 U.S. Code for more details.)
[Last updated in June of 2020 by the Wex Definitions Team]