The subpoena was first reported by The New York Times.
The source who spoke to CNBC confirmed, as reported by the Times, that the subpoena to Aon seeks a raft of documents about Aon’s dealings with Trump himself and the Trump Organization going back a decade, including communications involving all three of those parties.
The White House referred CNBC to the Trump Organization for comment on the subpoena to Aon. The Trump Organization did not immediately provide comment.
Cohen has been cooperating with multiple federal and state authorities as he prepares to begin serving a three-year prison sentence for a number of crimes, some of which relate to his work for Trump.
During his testimony before the House Oversight Committee last Wednesday, Cohen was questioned by New York Democratic Rep. Alexandria Ocasio-Cortez.
“To your knowledge, did the president ever provide inflated assets to an insurance company?” Ocasio-Cortez asked.
Cohen replied, “Yes.”
“Who else knows that the president did this?” Ocasio-Cortez asked.
Cohen then named three Trump Organization executives: “Allen Weisselberg, Ron Lieberman and Matthew Calamari.”
“And where would the committee find more information on this?” Ocasio-Cortez asked. “Do you think we need to review his financial statements and his tax returns in order to compare them?”
Cohen said, “Yes, and you would find it at the Trump Org.”
The Times story on Tuesday noted that the New York Department of Financial Services previously looked at the Trump Organization.
In 2017, the department examined Trump’s company’s longstanding dealings with the lender Deutsche Bank. That probe did not result in any sanctions on the bank.