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. It is an agency 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 IRS was created in 1862 to assess the nations first income tax to fund the American Civil War. The temporary measure funded over a fifth of the Unions war expenses before being allowed to expire a decade later. In 1913, the Sixteenth Amendment to the U.S. Constitution was ratified, authorizing Congress to impose a tax on income and leading to the creation of the Bureau of Internal Revenue, which later became the IRS.

The IRSs mission 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. Taxpayers can visit the official IRS website to pay their taxes, check their refund status, find IRS forms, and get answers to tax questions. The IRS also has taxpayer assistance centers located throughout the United States where taxpayers can receive in-person assistance with their tax-related issues.