The IRS is a bureau of the Department of the Treasury and one of the world's most efficient tax administrators. In 2004, the IRS collected more than $2 trillion in revenue and processed more than 224 million tax returns.

The roots of IRS go back to the Civil War when President Lincoln and Congress, in 1862, created the position of commissioner of Internal Revenue and enacted an income tax to pay war expenses. The income tax was repealed 10 years later. Congress revived the income tax in 1894, but the Supreme Court ruled it unconstitutional the following year.

The IRS Restructuring and Reform Act of 1998 prompted the most comprehensive reorganization and modernization of IRS in nearly half a century. The IRS reorganized itself to closely resemble the private sector model of organizing around customers with similar needs. To support its structure and ensure accountability, the IRS is divided into three commissioner-level organizations: Commissioner, Deputy Commissioner for Services and Enforcement and Deputy Commissioner for Operations Support