Short answers, pulled from the story.
The IRS traces its origin to July 1862, when President Abraham Lincoln and Congress passed the Revenue Act of 1862, creating the office of commissioner of internal revenue. The Bureau of Internal Revenue was formally renamed the Internal Revenue Service in 1953, with the name change finalized in Treasury Decision 6038.
For fiscal year 2023, the IRS collected approximately $4.7 trillion, which represents roughly 96 percent of the operational funding for the federal government. During fiscal year 2006, the IRS collected more than $2.2 trillion in tax net of refunds.
In 1894, the Supreme Court struck down a federal income tax in Pollock v. Farmers' Loan and Trust Co., ruling it unconstitutional without apportionment among states by population. The Sixteenth Amendment, ratified in February 1913, granted Congress the explicit power to impose an income tax without regard to apportionment, clearing the legal obstacle.
In 1969, Nixon directed the IRS to audit political opponents and opponents of U.S. involvement in the Vietnam War. The IRS's Special Services Staff compiled a target list of more than 1,000 organizations and 4,000 individuals. Commissioner Randolph W. Thrower refused and was fired; his successor Johnnie Mac Walters locked the list in his safe and later delivered it to Congress after Watergate broke.
With a salary of $200,000, Nixon paid $792.81 in federal income tax in 1970 and $878.03 in 1971. He claimed deductions of $571,000 for donating his vice-presidential papers. Reporter Jack White of The Providence Journal won the Pulitzer Prize for reporting on Nixon's returns.
The tax gap is the difference between taxes owed and taxes actually collected. As of 2007, the IRS estimated the U.S. Treasury was owed $354 billion more than it collected annually. For the years 2008-2010, the estimated gross tax gap was $458 billion, with a net tax gap of $406 billion after subsequent enforcement collections.