WASHINGTON — Mortimer Caplin, an eminence of tax law who propelled an often low-profile bureaucratic position into the national spotlight while serving as President John F. Kennedy’s hard-driving and charismatic commissioner of internal revenue, died July 15 at his home in Chevy Chase, Md. He was 103.

His son Lee Caplin confirmed the death but did not specify a cause.

Mr. Caplin brought political savvy and an extrovert’s flair to a somber profession mostly characterized by its fascination with loopholes and number crunching.

He was the star middleweight of a national championship boxing team as a University of Virginia undergraduate in the mid-1930s, and later graduated first in his class from the university’s law school. He was a beach master during the Normandy invasion in World War II and then continued a prominent career in private practice and academia.


He spent 33 years on the faculty of the U.Va. law school and jokingly credited his Internal Revenue Service appointment in 1961 to his ‘‘good judgment - the good judgment to have both Bobby and Teddy Kennedy as students at the University of Virginia and to pass them both.’’

In a career spanning seven decades, he also founded Caplin & Drysdale, a heavyweight Washington-based tax-law firm. But his legacy rests predominantly on his 3 1/2 years as a fiercely independent-minded IRS commissioner.

The agency had long drawn the ire of the public and private sectors for its arcane and seemingly malleable rules, its use as a political weapon by party leaders, and its periodically troubled leadership. In the early 1950s, the IRS was roiled by scandals involving bribery, embezzlement, and conflicts of interest.

Mr. Caplin ‘‘put a public face on a very different organization, a very professional organization,’’ a huge change from ‘‘10 years earlier when they were a bunch of thugs,’’ or, at least, were frequently perceived to be, said Charlotte Crane, a law professor at Northwestern University who focuses on tax history.


Mr. Caplin, with his ever-present bow tie, made the cover of Time magazine in 1963 and was presented as a fighter for a more enforceable and equitable tax code.

Through his work on a major tax overhaul, he clamped down on deduction abuse particularly by businessmen who scribbled from memory their travel and entertainment expenses. Mr. Caplin won a legislative fight to require that any expense over $25 be itemized.

‘‘The hunting lodge, the yacht, the safari,’’ he told Time, ‘‘they’re going to be out. But I can see $24.95 specials developing all over the country.’’

As commissioner, Mr. Caplin was a crucial backer of the centralized computer system in West Virginia known as the ‘‘Martinsburg Monster.’’ The National Computer Center, as it was formally called, replaced the ‘‘tired eyeball check,’’ where agents in more than 50 district offices manually examined tax forms.

The public initially balked at the automated system, fearing government overreach as the agency tracked each taxpayer with a number. But Mr. Caplin hailed Congress’s approval of the system in the final hours of the 1961 congressional session, saying that its passage meant that ‘‘taxpayers will be assured that no one is getting away with anything.’’

The system, which served as the basis for IRS data processing until the turn of the 21st century, started increasing revenue soon after its launch. In the Atlanta region, the only place the computer checked returns in its first year, tax collections rose 10.9 percent over the year before, compared with 5.4 percent nationwide.


Mr. Caplin also cooperated with his former student Attorney General Robert Kennedy on an effort to crack down on organized crime.

The value of property seized in gambling raids more than doubled from 1960 to 1963. Busts included what at the time was the biggest numbers raid in Virginia, where special IRS agents burst into a Loudoun County horse farm, arresting eight people and shutting down an operation that generated $4.5 million a year.

Mortimer Maxwell Caplin was born July 11, 1916, in New York City to Jewish parents. His father was a physical education teacher who became the city school system’s director of health education.

Mr. Caplin said his Depression-era upbringing, in which he saw educated adults reduced to menial jobs, had a major impact on his decision to turn to law as a vehicle for social change.

He was a 1937 graduate of U.Va., and a 1940 graduate of its law school, where he was editor in chief of the law review. He worked for Paul, Weiss, Rifkind, Wharton & Garrison, a top Wall Street firm, before entering the Navy during World War II.

His wife, the former Ruth Sacks, died in 2014 after 71 years of marriage. Survivors include four children, Lee Caplin of Coral Gables, Fla., Michael Caplin of McLean, Va., Jeremy Caplin of Earlysville, Va., and Cate Caplin of West Hollywood, Calif.; eight grandchildren; and three great-grandchildren. A daughter, Mary Ellen Caplin, died in 1977.


Mr. Caplin became a professor at U.Va.’s law school in 1950. Three years after joining the faculty, he completed a doctorate in law at New York University. In Charlottesville, Va., he was a partner at the law practice of William Battle, a prominent Democrat and John Kennedy presidential supporter who was crucial in backing Mr. Caplin for the IRS post.