Donald Trump’s Tax Returns: What We Could Learn From Them The real estate mogul said he is currently under audit.

 -- Donald Trump's refusal to release his tax returns, until he allegedly finishes being audited, has raised questions about his reticence and what could be learned from the documents.

Sources of income, any use of off-shore bank accounts and the overall health of his various businesses would likely be revealed, according to two legal experts.

"In terms of what could be in them -- it's anybody's guess," said political law expert Kenneth Gross. "There could be no problems. There could be problems on the amount of tax he's paying, deductions he's taken, income he's taken, any host of issues in the calculation of tax."

Prospect of Paying a Low Tax Rate

If Trump is paying a lower tax rate than expected, he wouldn't be the first presidential candidate to do so. Mitt Romney was criticized during the 2012 presidential campaign that he waited some time to release his returns, and when he did make them public, it revealed that he paid less than 15 percent.

Romney said in a Facebook post on Wednesday: "It is disqualifying for a modern-day presidential nominee to refuse to release tax returns to the voters, especially one who has not been subject to public scrutiny in either military or public service."

For Trump's part, he's made it clear that he has tried to pay as little as possible.

"I try very hard to pay as little tax as possible and have said that for the last two years," Trump said today on ABC News' "Good Morning America," saying that's "because this country wastes our money."

Under Trump's proposed tax plan, anyone making more than $150,001 would have a 25 percent income tax rate.

When asked on "GMA" to share his own tax rate, Trump said: "It's none of your business."

Historical Precedent of Releasing Tax Returns

Every president since Gerald Ford, who released a summary of his tax returns in 1976, has released their returns.

Hillary Clinton released her family's tax returns from 2007 through 2014, and they had previously released returns dating back to 1977. Her campaign states that their family paid an effective tax rate of 35.7 percent in 2014. Sen. Bernie Sanders released his 2014 tax return in April, showing that while the family's income put them in the 28 percent tax bracket, deductions brought them to an effective rate of 14.7 percent.

Assessing Trump's Wealth and Business Assets

There has been much speculation about Trump's wealth since his self-estimates place his net worth at $10 billion. Other outside groups, like Forbes, put his net worth at $4.5 billion.

Even if the tax returns are released, that doesn't mean the question of his true net worth will be solved, according to Rachel Stockman, an editor at LawNewz.

"He wouldn't be required to report [the actual value of his assets]. He would just have to report the money coming in and coming out of his businesses and whatever else he owns, including investments," Stockman told ABC News.

"It would give us a good indication, however, of the financial conditions of his various businesses," she said.

Stockman said she spoke to about half-a-dozen tax attorneys and only one said that she would advise her client to release their tax returns while under audit.

"The concern from tax attorneys was that public opinion could influence the auditors," Stockman said.