Some presidents took some significant tax cuts while others proved to be surprisingly generous with charitable givings. Here are six surprising things we’ve learned about past presidents from their taxes.

1. Franklin D. Roosevelt: 1933-45

FDR didn’t release his tax returns, but his presidential library later made many of them available. As it turns out, those returns would have caused quite the scandal if they had been released during his presidency, according to tax historian Joseph Thorndike. Though he strongly criticized other Americans for trying to get out of paying their taxes, FDR made a habit of minimizing his own. 

During his first term as president, he paid taxes at the rates in effect at the time he took office in 1933, even as Congress passed (and Roosevelt approved) tax hikes for everyone else. In FDR’s view, paying taxes at the higher rates would have effectively reduced his salary, a violation of a clause in the Constitution outlawing any reduction in a president’s compensation while in office.

2. Richard Nixon: 1969-74

In 1973, with the Watergate scandal heating up, tax experts called for an audit of President Nixon. The IRS refused, but one of the agency’s employees leaked information showing Nixon paid only $792.81 in federal income taxes in 1970 and $878.03 in 1971, despite income of more than $200,000. He also took a huge number of deductions, including $570,000 for the gift of his vice-presidential papers to the National Archives, which he apparently had his aide backdate to the previous year (before it became illegal for him to take the deduction). 

Nixon ended up releasing his tax returns going back to 1969, and was later hit with a tax bill of $471,431 plus interest. “People have got to know whether or not their president is a crook,” Nixon told reporters in November 1973, in the midst of the scandal over his taxes. “Well, I am not a crook.” He resigned less than a year later.

3. Ronald Reagan: 1981-89

Reagan’s 1981 tax return showed he paid taxes at an effective rate of 40 percent–the highest effective tax rate of any president from Nixon to Obama. But Reagan also took advantage of the signature tax cuts he passed while in office: In 1987, he paid only 25 percent of his income to the IRS. According to that year’s tax return, Reagan’s income that year included not only his presidential salary but also $1,312 in residuals from his movie career and $281 in royalties from his autobiography, Where’s the Rest of Me?

WATCH: Why Pay Taxes? Your Dollars at Work

4. George H.W. Bush: 1989-93

According to his 1991 tax returns, President George H.W. Bush gave nearly 62 percent of his $1.3 income away, making him by far the most generous recent president when it came to charitable giving. His favored causes included his alma mater, Yale University (specifically the Class of 1948 fund), the Barbara Bush Foundation for Family Literacy and the Desert Storm Foundation.

5. Bill Clinton: 1993-2001

In 1994, Bill and Hillary Clinton released years of their tax returns to satisfy persistent questions about the Whitewater Development Corporation, a failed real estate venture that some claimed involved illegal dealings by the Clintons. (The couple was never prosecuted, and three separate inquiries found no evidence they had done anything illegal.) Though their former partner in the deal had earlier claimed the Clintons lost no more than $13,500 in the Whitewater venture, suggesting they were trading some kind of political favors for a relatively risk-free investment, the couple’s tax returns from 1978 and 1979 showed they actually put enough money into Whitewater in order to claim $22,000 in related deductions.

6. Barack Obama: 2009-17

As a presidential candidate in 2008, then-Senator Obama released seven years of past tax returns. These showed that he and his wife Michelle had increased their charitable contributions significantly in recent years, as their income rose thanks to sales of his books Dreams From My Father and The Audacity of Hope. The biggest of the couple’s donations ($27,500 in 2005 and 2006) went to the Trinity United Church of Christ, where the Rev. Jeremiah A. Wright Jr. had been Obama’s pastor for 20 years. Wright’s controversial statements about the United States over the years had caused Obama some big headaches during the campaign, leading the candidate to distance himself from his former pastor.