The federal government has set the deadline for citizens to pay for their prior year’s income tax. The Congress has occasionally taxed citizens’ incomes since the Civil War. The Supreme Court declared it unconstitutional in the late 1890s. But in the Progressive Era, the Congress proposed and the states ratified the 16th Amendment, which empowers Congress to expressly tax individual’s incomes, from whatever source derived.
The Internal Revenue Service (IRS) Historical Timeline provides a basic history and function of national taxes. From the agency’s About page, you can glean much about the operation, tax collection, and enforcement mechanisms.