"The loss you are seeing in the 1995 returns might be a decreased loss, because his overall loss could have far exceeded his income. That means, according to the tax laws, he would be allowed to carry over the remaining portion of the loss to another year," Rosenfeld told CNBC. "This billion-dollar loss could be the tip of the iceberg of a far larger loss."

Joel Rosenfeld, an assistant professor at New York University's Schack Institute of Real Estate, speculated that the loss could well be more than a billion dollars.

The spotlight focused this past weekend on Donald Trump 's 1995 tax returns have supporters like former New York Mayor Rudy Giuliani calling Trump "a genius" — but, according to one tax expert who reviewed the documents, Trump's nearly $1 billion loss doesn't paint the whole picture. In fact, he stressed the loss could be far larger.

But without seeing earlier or subsequent tax returns from Trump, besides 1995, Rosenfeld's views are conjecture. Trump has broken with precedent for a presidential race by refusing to release tax returns, citing an audit by the Internal Revenue Service.

The 1995 tax returns and Trump's $916 million loss were first reported by The New York Times. Rosenfeld was also quoted in the Times' article. Trump campaign officials did not respond to CNBC's request for comment.

"I don't think the story stops there," Rosenfeld told CNBC. "In order to really get an assessment of the size of the loss, one has to look back prior to 1995. We need to know what created the loss, and the magnitude of the entire loss that time."



In order to answer those questions, Rosenfeld said you need to see the prior year's tax returns. "You need additional tax returns to really paint the picture of the true size of the loss. Trump could have sucked up the loss in prior years as well in multiple past returns, by offsetting income in those years."



The Trump organization is a limited liability corporation comprised of hundreds of companies. In Trump's financial disclosure forms that he filed to run for president, he accounted for some 500 entities.



"We know before 1995 he had the financial demise of his casinos, airline and the Plaza hotel. That is why we need to see the prior returns," said Rosenfeld.



At a rally in Pueblo, CO, on Monday, Trump was on the defensive, explaining the nearly billion-dollar loss was at the end of "one of the most brutal economic downturns" in U.S. history. He went on to blame the media, saying, "The news media is now obsessed with an alleged tax filing from the 1990s at the end of one of the most brutal economic downturns in our country's history." The Times confirmed the return with the accountant listed on the document.



Rosenfeld explained there are various ways limited to the real estate industry to create losses. "Failure, current operating losses enhanced by depreciation, interest on mortgages and various fees. Bottom line, this billion-dollar loss was a business disaster. Just how large, no one really knows. The loss could be much larger."