Trump's tax plan will boost American businesses, if it becomes law.

The White House on Wednesday unveiled in broad strokes its tax reform proposals, including a major reduction in the corporate tax rate, a one-time repatriation tax and a territorial tax system for American companies. The plan could be a boon for U.S. businesses, but if it expands the deficit as much as many analysts say it would, it doesn't do much in the long-term.

"What will be critical for businesses is whether this is a permanent tax cut and a permanent change to the tax code, or if this is going to be a 10-year or less approach, similar to the Bush tax cuts," said Michael Greenwald, partner at New York-based accounting and consulting firm Friedman LLP.

Tax reform is likely to be done through budget reconciliation, which requires only a 51-vote simple majority in the Senate but comes with some conditions -- namely, the Byrd Rule. Dating back to 1985, the Senate rule prohibits "extraneous" matters as part of reconciliation bills, including provisions that would increase the deficit beyond 10 years.

The Byrd rule is why the Bush tax cuts expired at the end of 2010.

"If [tax reform] is permanent, you might start to see businesses reorient how they are organized and how they fund their businesses, whereas if it's only 10 years or shorter, it's going to be less impactful, because nobody's going to make those kinds of changes if they don't believe that doing so isn't going to have adverse consequences," Greenwald said.

The administration's one-page Wednesday tax plan hardly provided enough detail for full analysis. It left out, for example, the rate at which a repatriation holiday would be enacted.

The plan Trump put out during the campaign would have slashed federal revenue by $2 trillion over 10 years, the conservative-leaning Tax Foundation estimated.

Both Wednesday's blueprint and the campaign platform entailed a 15% corporate rate.

Treasury Secretary Steve Mnuchin speaking at an event in Washington, D.C. ahead of the plan's unveiling said the White House would prefer tax reform to last beyond a decade but isn't tied to the idea, either.

"The goal is to make it permanent, but there's lots of levers here," he said. "If we have them for 10 years, that's better than nothing."

White House officials and Congressional Republicans are betting hard on dynamic scoring, which assumes tax cuts lead to economic growth. (Even with dynamic scoring, the Tax Foundation estimates the government would be out more than $1 trillion under Trump's plan.)

"Tax rate reductions, when you go from the worst in the world to something better, it's going to give us economic growth and we should account for that. We do in the House already use that kind of dynamic scoring," House Speaker Paul Ryan said at a legislative breakfast earlier in the day.

Addressing reporters on Wednesday, Mnuchin said the plan would pay for itself through growth combined with deduction reductions and closed loopholes.

"The economic plan under Trump will grow the economy and will create massive amounts of revenues, trillions of dollars in additional revenues," he said.

The Tax Foundation's Alan Cole explained in a recent blog post that achieving the amount of growth necessary to render a 15% corporate tax rate self-financing would mean an additional 0.9% in additional growth over the course of the decade. The conclusion: through tax cuts, such growth can't be achieved.

"In order to make a deficit-neutral cut in the corporate income tax rate, other deficit-reducing policies would be necessary," he said.

Stocks declined slightly on Wednesday after posting two consecutive days of gains. The S&P 500 dropped 0.05%, the Dow Jones Industrial Average lost 0.10%, and the Nasdaq was flat.

The potential explanation: businesses and investors still have a lot of questions.

"Is there anything that stands out as meaningful [about Wednesday's announcement]?" Greenwald said. "The fact that we don't have any details."