The Republican proposals sharply lower the top tax rate on the income that REITs and other businesses pass through to their owners and shareholders. Currently, those investors must pay taxes on that income at rates as high as 39.6 percent. Under the Senate provision, it would drop to 29.6 percent. (The House bill drops the rate even lower, to 25 percent.)

That’s a big savings, and a big advantage. Those receiving mortgage-interest income outside a REIT would have to pay taxes based on ordinary rates.

The Trump Organization is a partner in two of its largest properties with Vornado Realty Trust, a REIT based in New York City. In January, the White House appointed Vornado’s founder and chairman, Steven Roth, to develop a trillion-dollar infrastructure package as a leader of an advisory council that has since been abandoned.

Vornado has also been associated with Kushner Companies, helping bail out its stake in 666 Fifth Avenue, the Kushners’ flagship property, when it was in danger of defaulting on a more than $1 billion loan.

Kushner Companies has teamed up with another New York-based REIT, SL Green Realty Corporation, in several deals. They are collaborating on a development in Brooklyn, and SL Green lent Mr. Kushner’s firm $85 million in 2016 to refinance its slice of the former headquarters of The New York Times in Manhattan.

A Kushner Companies spokeswoman said the firm had not done any lobbying on the tax bill.

Kurt Koegl, a partner at the national accounting firm Marcum, noted that a lower corporate tax rate would enable other kinds of companies to better compete with REITs.