Every year, millions of Americans have to amass their financial records and fill out forms—or pay professionals to do it for them—in order to file their federal tax returns. It’s an annual ritual that traditionally takes place in the spring on or around April 15.

For those who grumble over having to contemplate those numbered boxes on the IRS Form 1040, they have William Howard Taft to thank. The nation’s 27th President, who served just a single term from 1909 to 1913, is probably best known for being the heaviest president in U.S. history as well as the first to ride in an official presidential limousine, and for his obsession with golf. But Taft also established the federal income tax as a permanent part of Americans’ lives.

Taft didn’t actually invent the idea of a federal income tax. That would be Abraham Lincoln, who in 1861 convinced Congress to pass the Revenue Act and impose a temporary 3 percent tax on incomes over $800, as an emergency measure to help finance the massive military expenditures required by the Civil War. That measure was allowed to expire in 1872.

The idea of a federal income tax resurfaced after the Panic of 1893, an economic downturn so severe that it caused a quarter of the nation’s labor force to lose their jobs. As Jeffrey Rosen notes in his 2018 biography of Taft, populist Democrats argued that the tariffs and excise taxes that the government depended upon for revenue put a disproportionate burden upon struggling farmers and workers, and argued for a tax that would capture more of affluent Americans’ income.

In 1894, they joined forces with progressive Republicans to pass legislation that created a 2 percent tax on incomes over $4,000, along with reduced tariffs. But that tax didn’t last long. In an 1895 case, Pollock v. Farmers’ Loan and Trust Company, the Supreme Court found that directly taxing Americans’ income was unconstitutional.

Even so, progressives’ desire to pass an income tax and cut back on taxing imports and sales taxes didn’t go away. When Taft succeeded Theodore Roosevelt as president in 1909, he faced a dilemma.

“Taft was a progressive Republican with moderate instincts,” Joseph J. Thorndike, director of the Tax History Project and author of numerous books and articles on the history of American taxation, explains. “He was also an institutionalist, especially with regard to the Supreme Court.”

Thorndike explains that in 1909, Taft was concerned that rambunctious lawmakers in both parties would push ahead with plans for a new income tax, ignoring the court’s 1895 decision that such a tax (at least as previously conceived) was unconstitutional. Taft believed that enacting such a tax could damage the court's authority.

A debate raged anew in Congress, with Democrats and progressive Republicans rallying to back a new income tax, while GOP leaders in both the House and Senate remained strongly against the idea.

“While support for the income tax skewed Democratic, there were a reasonably large number of Republicans who supported the levy, too,” Thorndike says.

Taft had been elected in part because people saw him as continuing the progressive reforms that Roosevelt had started, but he wasn’t a big fan of making Americans pay personal income tax as a way of “permanently restraining great wealth,” as Rosen writes. Instead, he saw personal income taxation as a power that should be used only in emergencies, such as wartime. Taft also worried that citizens who opposed personal taxation might simply refuse to pay and then commit perjury to evade the law.

“I don’t think Taft was ever really enthusiastic about the income tax, but he was aware that it had broad support in both parties,” Thorndike says.

Nevertheless, Taft saw a personal income tax as a political move that would help him to get Congress to pass the to get the tax on businesses that he needed to replace tariff revenue, according to David Sicilia, an associate professor of history at the University of Maryland who’s written about the origins of the federal income tax.

"Taft’s goals with the federal income tax were tariff and corporate tax reform,” Sicilia says. “But political horse trading and an increasingly progressive nation gave us something quite different."

To get what he needed, Taft had to figure a way around the Supreme Court. Otherwise, Taft feared that Congress would simply pass another tax bill and be batted down by the justices. He came up with an ingenious solution—combining tariff reduction legislation with a Constitutional amendment authorizing the federal government to collect income tax, which the court wouldn’t be able to overturn.

Some conservative opponents of the tax in Congress actually went along with Taft’s idea—apparently because they thought it would be dead on arrival. In July 1909, Congress passed the 16th Amendment to the Constitution.

To the shock of conservatives, the amendment was approved by enough state legislatures so by February 1913, U.S. Secretary of State Philander Knox certified the amendment's adoption. Not long after that, Congress enacted a federal income tax.

“Taft's plan succeeded—perhaps too well, from the perspective of many conservatives,” Thorndike says.

As W. Elliot Brownlee details in his book Federal Taxation in America: A Short History, the tax set a base rate of 1 percent tax on personal income, but also set a personal exemption of $3,000 that exempted virtually the entire middle class. For incomes above $20,000 it imposed an additional surtax of up to 6 percent. During the first several years of the tax, only 2 percent of U.S. households paid taxes. (Here’s the first federal income tax form from the National Archives.)

Initially, the federal tax day was March 1, but in 1918, Congress changed it to March 15. In 1955, Congress moved it back another month, to April 15.

The federal government has extended the traditional April 15 deadline for exceptional circumstances. In 1970, NASA arranged a last-minute extension for astronaut Jack Swigert because he'd forgotten to file his taxes before launching to space on board the fateful Apollo 13 mission. In 1980, Congress gave the families of Iranian hostages additional time to file their returns. In 1992, a similar extension on forms and tax payments was granted to some Los Angeles taxpayers who had been affected by rioting in that city. And, in 2020 and 2021, the IRS delayed the filing deadline for all Americans due to the disruption caused by the COVID-19 pandemic.