"The problem with all these plans is they are loosely specified," said Roberton Williams, a senior fellow at the nonpartisan Urban-Brookings Tax Policy Center, speaking generally of tax proposals from the 2016 presidential contenders. "The details aren't all there and you don't really know what they would do."
In its analysis of candidates' tax plans, the Tax Policy Center says that Trump's proposal will likely cost the U.S. Treasury money, but that it's impossible to say how much. Another Washington-based research group, the Tax Foundation, estimates that Trump's plan would reduce federal revenue more than $10 trillion over 10 years.
Another Trump proposal with impact that's hard to gauge: His plan would make it harder for high-income taxpayers to fully benefit from personal exemptions and deductions by steepening the eligibility curve for provisions of the tax code known as Pep and Pease. In 2013, Congress reinstated these limits for married couples with adjusted gross income of more than $300,000 a year or $250,000 for singles.
Though Trump doesn't spell out how much of a change he'd make to the Pep and Pease provisions, Williams said it would likely raise tax rates on high-income households. That's because while they'd still get some benefit from the remaining deductions such as mortgage interest and charitable deductions, those breaks wouldn't be worth as much as they are now, he said.
How much Trump's plan would benefit or hurt him directly remains unclear. The real estate mogul, who tweeted a photo of himself signing his mammoth tax return on October 15—the due date for taxpayers who received extensions—has yet to disclose his 2014 tax return to the public.
Trump's campaign spokeswoman, Hope Hicks, didn't respond to multiple e-mails asking when her boss plans to release his return. Though there is no legal requirement to do so, it has become traditional for the president and vice president, along with candidates for the White House, to make their tax returns public. So far, 2016 candidates who have done so are: Jeb Bush, Hillary Clinton, and Carly Fiorina.
Nitti said that a big drop in income-tax rates like the one Trump proposes will benefit the wealthy more than they could ever be penalized by the elimination of itemized deductions.
And Trump would eliminate the estate tax—another plus for wealthier Americans like him. The candidate himself is a trustee of multiple family trusts set up by his father to pass wealth onto heirs, according tothe candidate's July financial disclosures. That change could simplify the tax code because there would be less incentive to use its complex trust provisions and rules on valuing assets to lower the tax bite at death.
"The current code is crazy," Trump says in his new book. His goal, he writes, is to reduce the complexity and "put H&R Block out of business."
It's a catchy quote, but the reality is that Trump would still need approval from Congress to achieve a tax-code overhaul. And while many lawmakers agree with the concept of simplifying the tax code they haven't been able to reach a deal on how to do that.