By Richard Rubin

President-elect Donald Trump's charitable foundation engaged in self-dealing in 2015 and prior years, the foundation said in an Internal Revenue Service filing.

That self-dealing, which can lead to additional taxes and penalties, resulted from payments to "disqualified persons," or foundation insiders, according to the document. The filing -- the foundation's tax return for 2015 -- doesn't provide more details. Representatives for Mr. Trump didn't respond immediately to requests for comment Tuesday.

The form was posted on Guidestar, a website that compiles nonprofits' tax forms. Guidestar said it was submitted from the law firm representing the foundation and that it might not be the exact final version that gets submitted to the government.

"They admit at this point that there are problems with their prior returns," said Phil Hackney, a Louisiana State University law professor who has been examining the returns.

Mr. Trump's foundation has already admitted that it had made an improper donation to a political group associated with Florida Attorney General Pam Bondi in 2013, essentially making a payment that should have been from Mr. Trump's pocket directly. The new disclosure may cover more issues than that payment because it acknowledges problems in 2015.

Unlike in previous years, Mr. Trump's companies donated to the foundation, giving more than $600,000. Listed on the tax returns as recipients of the foundation's money were conservative groups such as the Media Research Center, Project Veritas and the American Conservative Union Foundation. Other recipients included the Apollo Theater Foundation, the Leukemia and Lymphoma Society and the New Jersey Boxing Hall of Fame.

The Trump foundation also reported receiving $150,000 from the foundation of Victor Pinchuk, a Ukrainian businessman.

The payment was "in support" of a video appearance by Mr. Trump in September 2015 at a conference sponsored by the Pinchuk foundation and Yalta European Strategy, another group Mr. Pinchuk founded, Thomas Weihe, head of the foundation's board, said in an email on Tuesday.

Mr. Pinchuk organizes the Davos-like conference each year. Mr. Trump said he had known Mr. Pinchuk for a long time and praised the Ukrainian tycoon as a "special entrepreneur" and a "tremendous guy."

Despite his statements in favor of Russian President Vladimir Putin, which have upset Ukrainians, Mr. Trump criticized President Barack Obama in the video-link appearance for being too weak and not doing right by Ukraine.

"Part of the problem that the Ukraine has with the United States is that Putin does not respect our president whatsoever," Mr. Trump said, saying he had very strong feelings toward Ukraine and lots of friends there.

Mr. Pinchuk, a Ukrainian tycoon married to the daughter of former Ukrainian President Leonid Kuchma, is one of the country's highest-profile philanthropists, contributing to the arts in Ukraine and to an array of causes outside the country.

"Mr. Pinchuk had met Mr. Trump some years ago in New York," Mr. Weihe said. "This is how the invitation for Mr. Trump to speak at the YES meeting came about."

Mr. Pinchuk's foundation gave at least $8.6 million to Bill and Hillary Clinton's foundation, contributing to the conflict-of-interest concerns that Mr. Trump raised during the presidential campaign. Mr. Pinchuk, whose fortune stems from a pipe-making company, served two terms as an elected member of the Ukrainian Parliament.

Mr. Trump now faces some of the same conflict-of-interest questions that Mrs. Clinton did because of the opacity of his finances and the breadth of the president's powers and ability to assist his own business interests.

Because it can get routine extensions from the IRS, Mr. Trump's foundation likely won't file its returns for 2016 until November 2017. That means the public won't know who donated to him during the presidential campaign and the transition until after he is in office.

"You'll eventually know, assuming that they're being forthright," Mr. Hackney said. "So there is reporting here that's a lot more transparent than contributions to the Trump Organization itself, which we can't see or know about, ever."

Paul Sonne contributed to this article.

Write to Richard Rubin at richard.rubin@wsj.com

(END) Dow Jones Newswires

November 22, 2016 11:55 ET (16:55 GMT)

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