Final answer:
The IRS was created by Congress, following the need for a federal agency to manage taxes after the 16th Amendment authorized Congress to impose income taxes. The IRS collects federal income taxes under a progressive tax system, where personal income tax comprises the largest revenue source for the federal government.
Step-by-step explanation:
Creation of the IRS
The Internal Revenue Service (IRS), which is responsible for tax collection and tax law enforcement, was created by Congress. This came as a result of the need for revenue to operate the government. The IRS's role is to collect federal income taxes from both individuals and corporations, as well as to manage taxes for social insurance and retirement benefits.
The first federal income tax was imposed in the 1860s, but a constitutional amendment was needed to grant Congress the power to levy this tax. It was the 16th Amendment, which took effect in 1913, that authorized Congress to impose income taxes.
It's important to understand that in the United States, a graduated progressive tax system is in place, meaning that as a person's income increases, so does the percentage of that income which is paid in taxes. The personal income tax is the largest single source of federal government revenue, although it represents less than half of all federal tax revenue.