The Internal Revenue Service (IRS) is, in its own words, "a bureau of the Department of the Treasury," organized to carry out the responsibilities of the secretary of the Treasury under section 7801 of the Internal Revenue Code.
The IRS states its mission as: "Provide America's taxpayers top quality service by helping them understand and meet their tax responsibilities and enforce the law with integrity and fairness to all." The agency says this mission statement describes its role and the public's expectation about how it should perform that role.
The IRS describes a division of roles in the 📝United States: Congress passes tax laws and requires taxpayers to comply, and the taxpayer's role is to understand and meet his or her tax obligations. According to the IRS, its own role is "to help the large majority of compliant taxpayers with the tax law, while ensuring that the minority who are unwilling to comply pay their fair share."
On statutory authority, the IRS explains that the secretary of the Treasury has full authority to administer and enforce the internal revenue laws and has the power to create an agency to enforce these laws, and that the IRS was created based on this legislative grant. The IRS also cites section 7803 of the Internal Revenue Code, which provides for the appointment of a commissioner of Internal Revenue to administer and supervise the execution and application of the internal revenue laws.