For example, Gary D. Cohn, the president of Goldman Sachs, who was recently appointed to lead Mr. Trump’s National Economic Council, will have to sell all his stock in Goldman. Or take Rex Tillerson, Mr. Trump’s pick to be secretary of state, who will be divesting his shares in Exxon Mobil. Ordinarily, doing so would cause them to have a tax bill worth tens of millions of dollars. Instead, they will most likely put their assets in index funds or in a diversified blind trust, and then pay the tax bill on those assets when they sell them.

Henry M. Paulson, the former chairman and chief executive of Goldman Sachs, is perhaps the most famous appointee to have used the tax deferral, when he became secretary of the Treasury under President George W. Bush in 2006. People noted at the time that Mr. Paulson was the beneficiary of a law that had been signed by his new boss’s father.

The tax treatment has been called a boondoggle for the rich. Ms. Warren, along with three other senators — Sheldon Whitehouse of Rhode Island, Tammy Baldwin of Wisconsin and Dianne Feinstein of California, all Democrats — have introduced legislation to limit to $1 million the amount of capital gains that can be deferred, preventing, as they put it, “billionaires from reaping outsized tax write-offs.”

A Wall Street Journal analysis suggested the executives could save tens of millions in dollars in taxes.

“It’s inappropriate for the federal government to provide excessive tax breaks to Cabinet members in return for complying with ethics rules,” Ms. Feinstein said in a statement last week. “Public service is an honor, and billionaires shouldn’t require federal tax breaks for their service.”

But the senators seem to not appreciate that the tax law is hardly an inducement to leave a high position for public service. To believe that the tax treatment is a huge boon would oddly assume that a chief executive was leaving for the government because he or she was preparing to dump all of the stock in their company in the next three months.