Presumptive Republican presidential nominee Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE is drawing scrutiny after reportedly using charity money to buy himself a signed football helmet several years ago.

Trump engaged in a bidding war at a charity fundraiser four years ago to get a Denver Broncos helmet signed by then-quarterback Tim Tebow and a Tebow jersey, The Washington Post reported Friday.

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Trump won with a bid of $12,000 at the auction in Palm Beach, Fla., and later posed with the helmet, but he didn't actually pay using his own money, according to the Post.

The Susan G. Komen organization, the breast-cancer nonprofit that hosted the event, received the money from the Donald J. Trump Foundation, a nonprofit charity he founded in 1987.

The Trump Foundation, where the businessman serves as president, is mostly funded with other people's money, and at the time of the auction, Trump hadn't donated to the foundation for three consecutive years, according to the Post.

The Post reported that it's unclear where the football paraphernalia has gone, with tax experts questioning whether the businessman violated IRS rules against charities being used for personal gain.

Trump praised Tebow multiple times on Twitter after the Heisman Trophy winner was traded from the Broncos to the New York Jets in 2012, before brief stints at the New England Patriots and Philadelphia Eagles.

.@TimTebow has tremendous talent and a proven ability to lead. He deserves to be in the @nfl. — Donald J. Trump (@realDonaldTrump) May 29, 2013