Republican presidential candidate Donald Trump speaks during a news conference at the Trump National Golf Club Westchester on June 7, in Briarcliff Manor, N.Y. (Mary Altaffer/Associated Press)

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DONALD TRUMP has spent a lot of time and effort branding himself as a great philanthropist. It seems he has put less effort into actually giving his own money away. The discrepancy provides one more reason that Mr. Trump should release his tax returns.

The Post reported in April that Mr. Trump claimed to have given $102 million to charity over the past five years, but that none of the donations his campaign listed appeared to have come from the candidate’s personal funds. Instead, he had his golf courses give away rounds for charitable raffles and other such things, and he had others fund his charitable foundation. Many of the recipients, meanwhile, appeared to be connected to his business and political interests.

Last month we learned that Mr. Trump did not give the $1 million donation he promised veterans during a highly publicized February campaign event until Post reporter David A. Fahrenthold started asking questions months later. Now the Huffington Post is raising questions about whether he donated proceeds from the sale of his book “Crippled America: How to Make America Great Again,” as he promised to do. Neither the Huffington Post nor we could get an answer from the campaign.

It is possible that Mr. Trump has donated more than the public record suggests. A major reason the public does not know is that a key piece of evidence is missing: Mr. Trump’s tax returns. Unlike every other major presidential candidate in modern times, he has declined to release them. Theories abound as to why. One is that they would show that he does not make as much money as he boasts. Another is that he might pay little or nothing in taxes. Yet another is that Mr. Trump simply is not generous, despite his assurances otherwise.

Candidates are expected to release their tax returns for a good reason. The full documents give the public a sense of presidential candidates’ personal financial dealings — how they conduct themselves and the relationships they have built outside of their responsibilities in public office. Since Mr. Trump has never held public office and campaigns on the fact that he is unusually competent in his financial life, it is all the more important that the public have hard data with which to assess his grandiloquent claims. That should start with his tax returns and include information on the performance of his closely held private businesses, to prove that his statements about their success are more than bluster.

Voters can review Hillary Clinton’s tax information going back decades. By contrast, Mr. Trump thus far has offered nothing but flimsy excuses.