His death was confirmed by his son Lee.
Caplin pursued tax cheats who were costing the government billions of dollars. He persuaded Congress, despite the opposition of corporate America, to require that expenses of more than $25 be itemized if they were claimed as tax deductions.
“The hunting lodge, the yacht, the safari, they’re going to be out,” he told Time magazine for a 1963 cover article. “But I can see $24.95 specials developing all over the country.”
Caplin also introduced a centralized computer system — known as the Martinsburg Monster, for the city in West Virginia where it was located — to audit returns swiftly and equitably. Revenue and compliance increased as a result.
So did the government’s take from illegal gambling and other illicit enterprises after the IRS joined forces with Attorney General Robert F. Kennedy to battle organized crime.
Even before he was appointed, Caplin echoed, with greater alarm, Will Rogers’ adage that “the income tax has made more liars out of the American people than golf has.”
“We have reached a danger point which strongly evidences an undermining of the tax morality of large numbers of people,” Caplin warned a congressional committee hearing on tax reform in 1958.
“They appear to be developing a lethargy over tax enforcement, reminiscent of the former widespread attitude under the Volstead Act,” he said, referring to the legislation intended to enforce the 18th Amendment, which banned the sale of alcoholic beverages.
At the IRS, he was credited with largely fulfilling his goal of making taxpaying less painful by being “both reasonable and vigorous,” and by administering the agency fairly. (When he was urged by the Kennedy White House to explore whether right-wing groups were abusing their tax-exempt status, he said, he made sure to look into liberal organizations, too.)
By mid-1964, when he stepped down, he estimated that 95% of taxpayers filed returns of their own accord. (The latest estimates suggest that about 82% of individual and business taxes are paid on time and voluntarily — a higher percentage than those in most other countries.)
“Taxpaying isn’t gamesmanship,” Caplin told Life magazine in 1963. “It’s citizenship.”
Caplin, who served under Presidents John F. Kennedy and Lyndon B. Johnson, became commissioner in early 1961. He was a seasoned lawyer and professor, but was not necessarily viewed as a natural for the job. A few political connections may have helped.
While teaching law at the University of Virginia, he also practiced law with William Battle, who had helped rescue Kennedy when he was marooned in the Pacific during World War II, and who managed Kennedy’s 1960 presidential campaign in Virginia.
Caplin said his job prospects had also improved because of his good judgment — “the good judgment,” he said at the time, “to have both Bobby and Teddy Kennedy as students at the University of Virginia and to pass them both.” (“Bob didn’t volunteer very much, but he was a better student than Ted,” Caplin said.)
Mortimer Maxwell Caplin was born July 11, 1916, in Brooklyn to Daniel and Lilian (Epstein) Caplin.
His father, a physical education teacher who became an assistant director of health education for the New York City public schools, was described by Time as the “white sheep” among his siblings. One of Mort’s uncles was imprisoned after being implicated in crooked card games; another was killed in 1923 in a gangland shooting on the Lower East Side.
Caplin said his father had encouraged him to be a lawyer and began taking him to local Democratic clubhouses when he was 4 years old.
After completing John Adams High School in Queens, Caplin graduated with a Bachelor of Science degree in economics and political science in 1933 from the University of Virginia, where he was first in his class, and went on to earn a law degree there.
While in college, he won the NCAA middleweight boxing championship with a broken bone in his right hand.
He clerked for a federal judge, Armistead Dobie; practiced law in New York at what became known as Paul, Weiss, Rifkind, Wharton & Garrison; and enlisted in the Navy. In World War II, he served on Omaha Beach during the Allied landings.
He returned to the law firm and then, in 1950, joined the University of Virginia School of Law as a professor. He taught there until 1961. He was a visiting professor from 1965 to 1987 and a major benefactor of the university.
Caplin later completed a doctorate in law at New York University Law School and, after leaving the IRS, formed a tax law firm with Douglas Drysdale, another Virginia graduate, in Washington.
He married Ruth Sacks, a painter, designer and arts advocate, in 1942; she died in 2014. In addition to his son Lee, he is survived by two other sons, Michael and Jeremy; a daughter, Cate Caplin; eight grandchildren; and three great-grandchildren. A daughter, Mary Ellen Caplin, died in 1977.
Caplin often said that he owed much of his success in Washington to following the advice of his college boxing coach:
“Punch hard, punch first and keep on punching.”
This article originally appeared in The New York Times.