State prosecutors in Manhattan investigating former President Donald J. Trump and his family business are examining the extent to which Mr. Trump handed out valuable benefits to some of his executives and whether taxes were paid on those perks, according to people with knowledge of the matter.
The scrutiny of how the Trump organization handled what are known as fringe benefits is a growing aspect of the broader investigation.
As part of that line of inquiry, the prosecutors from the Manhattan district attorney’s office recently subpoenaed the records of an Upper West Side private school, seeking information about tuition payments Mr. Trump made on behalf of one of his top executives, according to two of the people familiar with the matter.
The subpoena sought information from Columbia Grammar and Preparatory School related to tens of thousands of dollars in tuition payments that Mr. Trump made over several years for at least one grandchild of the Trump organization’s longtime chief financial officer, Allen H. Weisselberg.
Mr. Weisselberg, who has not been accused of any wrongdoing, has become a focus for prosecutors as they mount an aggressive effort to gain his cooperation against Mr. Trump and the Trump Organization, people with knowledge of that effort have said.
But prosecutors’ interest in any fringe benefits Mr. Trump may have provided to his employees is not limited to Mr. Weisselberg. The investigators, working for the Manhattan district attorney, Cyrus R. Vance Jr., have also asked the Trump Organization to turn over documents related to any benefits Mr. Trump or the company provided to some other employees, according to two of the people with knowledge, though it is unclear whether the company awarded any such benefits.
Mr. Vance’s investigation is also focused on whether Mr. Trump and the company manipulated property values to obtain certain loans and tax benefits, among other potential financial crimes.
The subpoena to Columbia Grammar, in addition to seeking information about the Weisselbergs, also referenced tuition payments for Mr. Trump’s teenage son, Barron, who attended the school until he finished the fifth grade.
There is no indication that the prosecutors suspect wrongdoing related to those tuition payments.
The subpoena, which was reported by The Wall Street Journal, appears to be part of the broader effort in Mr. Vance’s office to assemble a picture of Mr. Weisselberg’s finances. Prosecutors have also subpoenaed his personal bank accounts.
The focus on the tuition — and other potential fringe benefits — suggests that the prosecutors are examining whether Mr. Weisselberg paid taxes on the tuition Mr. Trump paid.
Fringe benefits are special perks employers give to their employees such as cars, flights and club memberships. In general, those benefits are taxable, though there are some exceptions. Companies are typically responsible for withholding such taxes from an employee’s paycheck.
If a review of Mr. Weisselberg’s business or personal affairs uncovered tax evasion or any other wrongdoing, the prosecutors could then use that finding to press him to cooperate as they seek further information about the Trump Organization’s financial history. When seeking to turn an insider into a cooperating witness, prosecutors often seek leverage over the person, including any evidence of past wrongdoing, and then typically offer leniency in exchange for testimony or assistance.
Mary E. Mulligan, a lawyer for Mr. Weisselberg, declined to comment, as did the Trump Organization, though in the past Mr. Trump has claimed the investigation is a politically motivated fishing expedition. A spokesman for Mr. Vance, a Democrat, also declined to comment.
A lawyer for the school, Frank Perrone Jr., said that he could not comment other than to say that the school would cooperate with any investigation or request made by the authorities.
Mr. Weisselberg, an accountant who got his start working for Mr. Trump’s father, Fred, would be an ideal witness to guide the prosecutors through the Trump Organization, having managed the company’s finances for decades.
Prosecutors have also questioned Mr. Weisselberg’s former daughter-in-law, Jennifer Weisselberg, who is in the midst of a contentious court battle with her ex-husband, Mr. Weisselberg’s son Barry, over custody of their children. Barry Weisselberg manages the Trump Wollman Rink in Central Park.
Ms. Weisselberg has said that prosecutors had asked her about the tuition payments as well as gifts Barry Weisselberg received from Mr. Trump, including an apartment on Central Park South and several cars that were leased for them.
If the Weisselbergs lived rent-free for several years, the apartment, like the tuition payments, could be considered taxable income.
Tuition at Columbia Grammar currently costs about $55,000 a year. The school, which dates back to the 18th century, counts among its alumni the novelist Herman Melville; Peter Gelb, the general manager of the Metropolitan Opera; and the actress Sarah Michelle Gellar.
Ms. Weisselberg said in an interview that either Mr. Trump or her former father-in-law had paid her children’s tuition since 2012. She said that the tuition payment had been part of her ex-husband’s compensation and that he would pick it up directly from the Trump Organization.