For these reasons, the foundation’s tax returns contain clear misrepresentations. An officer or trustee of every foundation must sign the returns “under penalties of perjury.” Given the explicit questions that the tax form asks, it is hard to believe that the foundation omitted so much relevant information by mistake. The foundation’s governing board consists of Mr. Trump; his children Donald Jr., Eric and Ivanka; and a Trump Organization employee. They were advised by an accounting firm, to which the foundation paid a $5,000 fee in recent years. If the Trump family failed to understand the questions, their accountants could have explained.

While most charity board members are loyal fiduciaries serving the public good, some abuse the trust that society places in these institutions. The rules for private foundations are strict: Congress was worried that wealthy individuals would use their foundations for private gain. At the same time, the rules encourage the great generosity of philanthropists.

The law demands transparency to make sure charitable organizations deserve the favorable tax treatment they receive. While Mr. Trump has refused to release his personal tax returns for public inspection, investigation of the foundation’s returns show that he has not been forthcoming with the tax authorities.

The foundation’s returns also tell us something about Mr. Trump’s charitable giving, which his personal returns would more fully reveal: He may not be very generous. Mr. Trump’s most recent contribution to the foundation was $30,000 in 2008. No member of the Trump family has made a donation since. The candidate may have given to other charities directly, but he will have to release his personal returns for voters to know for sure.

Violations of these rules are an affront to all charities. The I.R.S. and the attorney general of New York, Eric Schneiderman, who is investigating the foundation to determine whether it complied with state law, should hold it to the highest standard. If the reported violations prove true, the foundation does not deserve its charitable or tax-exempt status.

Americans who give to, volunteer with, or depend on charities should know that politicking and self-dealing by charities are never acceptable. The candidate’s apparent disregard for the law does not bode well for a Trump administration.