During a trial before the tax court last year, Ms. Crile, whose work has focused on subjects like the Persian Gulf war of 1991 and the abuses at Abu Ghraib prison, described a dogged career of more than 40 years that has been more successful critically than financially. From 1971 through 2013, court papers said, she earned $667,902 from the sale of 356 works of art — or an average income of a little less than $16,000 per year — and, like many artists, she wrote off expenses from her work, like supplies, travel and meals, on her taxes. Only three years of her art career have been profitable, court records showed, and her reliable income came from teaching at Hunter, where she began part time in 1983 and became a tenured professor in 1994.

Image Susan Crile, a painter and printmaker who teaches at Hunter College, was accused by the I.R.S. of underpaying her taxes. Credit... Constance Kheel

The I.R.S., which accused Ms. Crile of underpaying her taxes by more than $81,000 from 2004 to 2009, argued that based on several factors, such as her lack of a written business plan, her work as an artist was “an activity not engaged in for profit” and that she could not claim tax deductions in excess of the income she made from her art. Further, in a claim that alarmed many in the art world, the I.R.S. contended that Ms. Crile’s legal position that she was both an artist and a teacher was “artificial” and that she made art primarily to keep her job as a teacher. (Hunter College requires its studio-art teachers to exhibit their work but does not require them to sell.) The agency argued that for tax purposes, Ms. Crile’s profession should be that of a teacher, and that her art-related expenses should have been filed not as business expenses but as unreimbursed employee expenses.

But Judge Albert G. Lauber of the tax court ruled Thursday that Ms. Crile had “met her burden of proving that in carrying on her activity as an artist, she had an actual and honest objective of making a profit” and therefore under tax law should be considered a professional artist.

Robert Storr, dean of the Yale School of Art, who testified on Ms. Crile’s behalf, said Monday that the ability to deduct art-related expenses — in art careers that might generate little money — was “one of the last remaining areas where the federal government cuts artists any slack to allow them to do what they do,” and that its protection was crucial.

Micaela McMurrough, a lawyer at Cravath, Swaine & Moore who represented Ms. Crile, said one of the key points argued in the case was that “art is not a business like other businesses.” “And I think that’s what this decision reflects, to a large extent,” she said.