The Internal Revenue Service (IRS) is the revenue service for the United States federal government, responsible for collecting U.S. federal taxes and administering the Internal Revenue Code, the main body of the federal statutory tax law. The IRS is a bureau of the Department of the Treasury and led by the Commissioner of Internal Revenue, who is appointed to a five-year term by the President of the United States. The duties of the IRS include providing tax assistance to taxpayers, enforcing tax laws, and processing tax returns.

The mission of the IRS is to provide Americas taxpayers top quality service by helping them understand and meet their tax responsibilities and to enforce the law with integrity and fairness to all. The IRS is headquartered in Washington, D.C., and does most of its computer programming in Maryland. It processes paper tax returns sent by mail and e-filed tax returns at three IRS center locations: Austin, Texas; Kansas City, Missouri; and Ogden, Utah.

Taxpayers can visit the official website of the IRS to pay their taxes, check their refund status, find IRS forms, and get answers to tax questions. The IRS also has a toll-free number (1-800-829-1040) and a TTY number (1-800-829-4059) for taxpayers to call for assistance.