Republican presidential candidate Donald Trump still refuses to release his tax return, so there is no way of knowing just how much the Trumps' donate to charity. But Trump's son Eric isn't as sure as he once was about how much they give away.

Trump has stated from the campaign podium that he gives "millions" to charity each year. He's sworn to donate earnings from “The Apprentice,” Trump Vodka, Trump University, as well as several books. According to David Fahrenthold's dogged investigation for the Washington Post, Trump should have given over $8.5 million. Yet, when Fahrenthold called over 200 major national charities, he found only $10,000 in charitable donations from Trump. In fact, the investigation shows that Trump himself hasn't given since 2008.

Trump’s campaign said that he has given $102 million in charitable gifts, but WaPo couldn't find the donations anywhere. Only then did the campaign clarify that the donations weren't actually cash given to charities, but things like free golfing and land "conservation easements."

Just last week Trump's son Eric said that his father gives "millions and millions and millions" to charity. In fact, the younger Trump said that his father gave "hundreds of thousands" to his own charity. He couldn't give exact figures but swore he would get back to WaPo. Then he emailed back and said, "We are going to maintain anonymity."

As it turns out, Eric Trump isn't so sure about how much his father has contributed to the charity after all.

"I’m sure there have been but without going back through 10 years, I wouldn’t remember check for check off the top of my head," Eric Trump wrote in an email. He was unable to name a single instance when Trump gave to the charity.

"I have a lot going on — I just don't have the time. Good luck with the story," he wrote.

This week, a watchdog group has also asked the IRS to look into Trump's use of funds from his own charity to purchase a signed football helmet from former NFL player Tim Tebow.

"What's unambiguous is that Mr. Trump ... manager and fiduciary of the Foundation's charitable assets, used Foundation dollars to purchase football memorabilia that he personally coveted," Brad Woodhouse of the American Democracy Legal Fund, wrote in the letter to the IRS.

The investigation is ongoing, at least until Trump releases his taxes and can prove the statements he has made are true.