Comprehensive tax reform is so complex that it has defied Congresses and presidents since Reagan. Tax law is riddled with loopholes embedded in the economy and defended by beneficiaries.
Some fundamental questions remain unanswered within the Trump team. For instance, it is unclear if Trump would support a plan that adds to the budget deficit. Past tax reform efforts have tried to be "revenue neutral."
Trump also has sent mixed messages on Ryan's proposed "border adjustment tax" that would end the corporate deduction for import costs and make export income tax-free, aiming to boost exports and raise new tax revenues.
The Trump team is heavy on Wall Street experience, but short on tax expertise. At Treasury, Mnuchin is the only Senate-confirmed political appointee in place. The job of Treasury assistant secretary for tax policy is unfilled.
A person familiar with the hiring process for the job said: "Treasury needs more capable tax expertise ASAP, or the White House will yank total control for tax reform from the department for the rest of the year, maybe beyond."
Mark Mazur, who held the Treasury tax job under former Democratic President Barack Obama, said Mnuchin has too much on his plate to concentrate fully on taxes.
Mnuchin has praised Treasury's 100 tax policy career staff, but they can only offer options to Trump appointees, said Mazur, now director of the nonpartisan Tax Policy Center.
"The political appointees are the ones who need to turn the crank on the sausage-making machine," Mazur said.
This article was provided by Reuters.