The Washington Post's David Fahrenthold has been doing yeoman's work researching and reporting on Donald Trump's charitable foundation and his personal finances, uncovering what Trump is trying to conceal by refusing to release his tax returns. The latest: Trump may have directed payments to his foundation in an act of possible tax evasion.

One of the questions surrounding the Trump Foundation is why Trump hasn’t contributed any money himself since 2008. Washington Post reporter David Fahrenthold may have found the answer: Because Trump was reportedly directing money owed to him or his businesses to the foundation.

The laws governing the diversion of income into a foundation were written, in part, to stop charity leaders from funneling income that should be taxed into a charity and then using that money to benefit themselves. Such violations can bring monetary penalties, the loss of tax-exempt status, and even criminal charges in extreme cases.

According to Fahrenthold’s sources, Trump has directed approximately $2.3 million worth of payments he was owed personally to the foundation. The problem for Trump is that he is still required to pay taxes on that income.

But the Post was stonewalled when it sought proof that Trump paid the taxes he owed:

Could he provide proof of that tax payment?

“Absolutely not,” [Adviser Boris] Epshteyn said.

The only way to know for certain whether Trump has complied with the law is for him to release his tax returns for public scrutiny. It is long past time for him to do so.