There's a lot you can learn from looking at a person's tax return. You can tell how much a taxpayer gave to charity; what their sources of income are; whether they're married or divorced. You can learn how much or how little they made, whether they moved for a job and (sometimes) whether they have children.

At least, you can learn these things from looking at the tax returns of an ordinary worker. When it comes to President Donald Trump and taxpayers at his rarified income level, a tax return can deliver plenty of personal information but still lack some of the most tantalizing stuff -- their total net worth, for instance, or what real estate they own.

"I think [President Trump] is worried about two things: One, the income is probably lower than his pride will be able to deal with, and I think the charitable deductions will be way lower [than he has claimed]. I think that's going to be an embarrassing number for him," said Mark Matthews, an attorney at tax law firm Caplin & Drysdale. (Matthews, like all the tax attorneys consulted for this article, made his assessment based on media reports about Mr. Trump's wealth and his own knowledge of the tax code.)

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The first billionaire president, who made his business acumen a focal point of his presidential campaign, Mr. Trump now faces the prospect of a Democratic majority in the House of Representatives examining those claims through his tax documents. Accounting experts and tax attorneys told CBS MoneyWatch what Mr. Trump's tax returns might hold for Americans—and what they won't show.

What's in and what's out

"It's not so much about what's on the return that matters -- it's about what's not on the return," said Bruce Dubinsky, managing director of Disputes and Investigations at Duff & Phelps, a corporate advisory firm. If a taxpayer is known to own many business entities, like resorts, hotels or country clubs, those items should appear on the tax returns, he said.

Dubinsky, who said he has prepared about 10,000 tax returns for high-net-worth clients over his career, estimated that Mr. Trump's return at "probably 200 to 300 pages long, with multiple schedules that have summary-level detail."

Signing my tax return.... pic.twitter.com/XJfXeaORbU — Donald J. Trump (@realDonaldTrump) October 15, 2015

The operative term here is "summary." A tax return lists how much income a person made from a variety of sources, including a business, but it does not demand documentation to back up that figure. (If the IRS asks to see documents, that's a sign you're being audited.)

Marriage or divorce

Until this year, taxpayers could deduct alimony payments from their income—and seeing someone's payments, year over year, might provide a hint about their broader financial situation.

"If someone is receiving $2 million a year in alimony, it's a clue that the person paying it has at least that much coming in every year," said Dubinsky.

Mr. Trump reached alimony agreements with both of his ex-wives, which his tax returns could corroborate. They could also confirm or refute certain media reports, such as whether Mr. Trump ever made good on a reported threat to withhold alimony from Marla Maples, his second ex-wife.

Broader details, such as the particulars of a divorce settlement, are another matter. Mr. Trump's two divorce settlements remain sealed.

Gifts to charity

Charitable donations appear regularly on tax returns for the roughly 30 percent of Americans who itemize their deductions. The IRS form doesn't go into detail, however. There are only two lines: one for donations in cash or check, and another for donations made in any other form (such as donations of real estate, stock or art.)

Such a line would be a starting point to request tax returns from linked accounts—such as foundations that received his contributions. And it would not necessarily be complete since there are ways to structure charitable donations that don't require an individual to report them. The Trump Foundation is shutting down, but Mr. Trump could also have charitable trusts, and those trusts' contributions to causes would not be reported on a tax return, said Dubinsky.

Gifts—not to charity

Gift taxes, one line of inquiry used in The New York Times' recent investigation of Fred Trump's real estate empire, could be similarly fruitful for his son. Gift tax returns could, for instance, show whether Mr. Trump has given away any assets and whether he has placed any into trusts, said Beth Kaufman, an attorney at Caplin & Drysdale.

The IRS requires people to report gifts anytime they give away cash or goods valued at more than $15,000, and report it on a completely separate form from the 1040. The gift tax return is obscure enough that it's only a concern for the wealthy.

"Your run-of-the mill person never files one in their entire life; your millionaire or billionaire files one every year," Kaufman said.

Foreign income

The U.S. taxes income its citizens earn anywhere in the world, which means money earned abroad must be reported. Americans are also required to report foreign bank accounts to the Treasury.

Interest earned on foreign bank accounts would also be reported as "interest income" on a tax return, though the form itself would not indicate if the interest income came from a domestic or foreign bank.

For owners of companies outside the U.S., it's more complicated. American owners of foreign corporation's aren't always required to report that income, Dubinsky said: "If you own a hotel in Singapore, and that's set up as a foreign corporation, there are rules that maybe you don't need to report that income."

Foreign income reporting also runs into the same problem as before: It's income, not wealth. And finding out how much interest someone earned on an account won't tell you how much that account is worth. A return could show interest income of $100, "but you don't know if that's one night's interest on a million dollars, or a year's interest on $3,000," as one attorney put it for CBS MoneyWatch.

Deductions

Charitable donations are the best-known, but taxpayers have a number of expenses they're allowed to deduct from income, reducing the taxes they pay. A loss from an investment or a business is one such deduction—and Mr. Trump reported business losses on the partial tax returns for 1995 and 2005 that have become public. His 1995 loss, in particular, was listed at $916 million -- "so huge that he could conceivably have used them to avoid paying any federal income taxes for nearly 20 years," CBS MoneyWatch previously reported.

High medical expenses, the costs of moving for work, mortgage interest on buildings you directly own, and property taxes and local taxes could all count as deductions until recent changes under this year's GOP tax cuts. But they're not likely to appear on the president's tax returns, experts say, since much of his property is owned via more than 500 limited-liability corporations—each of which has its own income, expenses and business records. Getting a full picture of business activity would require not just the tax returns from those LLCs but a complete accounting record as well.

For any congressional committee looking into the president's finances, Mr. Trump's tax returns would be just a starting point.

"They're going to have to dig down into returns filed by LLCs, partnership returns. Almost none of that is copied on [Mr.] Trump's returns," Kaufman said. "I think there are going to be waves of requests to get into this."