The Treasury Department in Washington. (Andrew Harrer/Bloomberg News)

The Treasury Department late Friday proposed rules for a tax on the endowments of private colleges and universities, but higher-education experts say the guidelines raise questions more than they provide answers.

A provision in the sweeping 2017 tax law imposes a 1.4 percent excise tax on investment income at private schools with at least 500 tuition-paying students and endowments worth at least $500,000 per student. The Internal Revenue Service anticipates that about 25 to 40 institutions will be affected.

“Each college and university across the country is uniquely organized, and the proposed regulation is likely to have disparate impacts,” said Liz Clark, vice president of policy and research at the National Association of College and University Business Officers, a trade group. “It will likely take several weeks or more to fully understand the effects.”

Higher-education leaders have been vehemently opposed to the tax, arguing that it sets a dangerous precedent and could deprive colleges of revenue or drive up costs for students.

Colleges and universities maintain endowments, a collection of tax-exempt donations and investments, to pay for salaries, research, financial aid and other expenses. Large portions of endowments are restricted to uses that donors stipulate. The money also helps colleges weather ups and downs in economic cycles.

Still, as tuition at many well-heeled universities has climbed, lawmakers have accused wealthy schools of hoarding cash while middle-class families struggle to cover the cost of attendance. Yet the revenue from the endowment tax will not be used to lower the cost of higher education but instead to offset corporate tax cuts.

Republican lawmakers who backed the provision said it would put university endowments on equal footing with private foundations that are also taxed.

The 58-page draft rule certainly relies on some of the guidelines that govern private foundations. Colleges, for instance, can carve out 1.5 percent of their total net investment income from the calculation of what they might owe.

Like private foundations, schools would also be taxed on interest, dividends and rental income. That means colleges that provide their own student loans would have to pay taxes on the interest it yields. The money schools receive from students living on campus would also be considered taxable investment income.

Meanwhile, dorms, athletic facilities and other campus buildings would be exempt from taxation if 95 percent of their total use is for educational purposes.

The IRS exempts assets it considers essential in carrying out a college’s educational mission, but higher-education experts question the agency’s reasoning. Providing financial aid should be a clear part of that mission, as should providing housing at a residential college, experts say.

“The regulations pretty much make clear that the tax is going to harm students and families by imposing a direct cost on the affected schools and an indirect cost from the administrative burden,” said Steven M. Bloom, director of government relations at the American Council on Education, an organization representing the ­higher-education community. “It is enormously complicated.”

Treasury and the IRS are seeking comments from colleges and universities within the next three months on whether student loan interest, rental income and other assets should be exempt from taxation. Those comments could simplify the regulations.