On Wednesday, President Donald Trump will unveil a hard-negotiated and sweeping Republican plan to simplify the tax code and cut taxes for millions of families at an event in Indiana. “We’ll be releasing a very comprehensive report,” he said this week, speaking with reporters. “It will be a very, very powerful document.” Yet, despite those promises and even after months of backroom talks between the so-called “Big Six” Republican negotiators, any number of fundamental questions about the tax-reform effort remain impossible to answer—like how many tax brackets there will be, what level of earnings will fall into them, how much money the plan will raise, and whether wealthy Americans will get a bigger tax cut than middle-class families.

The Republican blueprint, as a general point, simplifies the code and cuts rates. There will be three brackets—at 12 percent, 25 percent, and 35 percent—though if necessary there might be a fourth bracket at some higher rate. Those brackets will start and end at dollar figures to be determined later. The proposal also doubles the standard deduction that most Americans take; increases the child tax credit by an unspecified amount; eliminates the alternative minimum tax; and gets rid of many itemized deductions, save for those for mortgage interest and charitable giving, as well as incentives for work, higher education, and retirement.

On the corporate side, Republicans are calling for slashing the top tax rate to 20 percent from 35 percent. The plan would also bring the top “pass-through” business rate down to 25 percent from its current level of 39.6 percent. That is the top rate that sole proprietorships, partnerships, and S corporations—meaning many small businesses—pay. It would also encourage businesses to bring back profits stashed overseas with a special rate cut.

The cuts will revitalize small businesses, aid the middle class, and boost job-creation and economic growth, Trump has promised. “America has the highest business tax rate in anywhere in the developed world. We’re the highest-taxed nation in the developed world, and I think in the undeveloped world too,” he said. “But you know, I have to be very accurate with these people because they’ll start claiming all sorts of things. So we’ll just keep it in the developed world.” (The United States does have the highest statutory corporate tax rate on Earth, but its effective average tax rate on corporations is not the highest in the developed world. Nor is the United States close to the highest-taxed nation, as a general point.)

What will all this add up to? How big will the tax cuts be? Would Trump himself pay more in taxes? At the moment, many crucial details remain unknown and it is difficult to say what outcomes they would lead to.

First and foremost, the unified plan—negotiated by Treasury Secretary Steven Mnuchin, Gary Cohn of the National Economic Council, Ways and Means Chairman Kevin Brady, House Speaker Paul Ryan, Senate Majority Leader Mitch McConnell, and Orrin Hatch, the head of the Senate Finance Committee—does not specify how much the tax reform would cost, with the range of possibilities extending into the many trillions of dollars. Senator Bob Corker of Tennessee has indicated that Republicans would need to eliminate deductions and loopholes worth $4 trillion to make up for the reduction in tax rates in the plan—deductions and loopholes that the plan does not enumerate. External analysts have suggested that the Republican wish list would cost something like $5 trillion over a decade, with the current Republican budget blueprint giving them only $1.5 trillion of room to maneuver. How Republicans might make up those multitrillion-dollar differences remains unclear.  

Another question is how much growth would make up for any revenue losses, and how much growth might figure into the Republican accounting process. Trump has indicated that the tax plan would boost growth up to as much as 6 percent a year. “The jobs will start pouring in from all over the world coming back to our country. They’ve left our country, so many of the jobs, and they’ll be coming back in because we have a non-competitive tax structure right now, and we’re going to go super-competitive,” he promised this week. Republicans have indicated the plan might be revenue-neutral, after accounting for souped-up economic growth. But economists broadly describe 6 percent growth as fantastical, and argue that tax cuts do not pay for themselves.

Then, there is the question of how much of a tax cut the middle class would get. “We will cut taxes tremendously for the middle class—not just a little bit, but tremendously,” Trump said this week. The proposal would actually increase the tax rate on the lowest tax bracket; a married couple filing a joint return last year paid a rate of 10 percent on their first $18,550 in taxable income. That rate has jumped to 12 percent, up to some unspecified level of income, in the Republican plan. Still, the overall initiative would likely dramatically increase the number of federal filers not paying any income tax—Mitt Romney’s infamous “47 percent”—given that it expands the standard deduction, and because of the expansion of the child tax credit. How much less the average family would pay remains unclear.

Finally, it remains impossible to tell just how much the rich would benefit. Earlier analyses of Congressional Republican and White House tax plans showed that the wealthiest Americans would see the biggest gains from such deep rate cuts, as well as proposals like the elimination of the estate tax and the lowering of the pass-through rate. (The plan would take unspecified steps to make sure that wealthy Americans did not restructure their earnings to take advantage of the 25 percent rate.) That said, efforts like repealing the alternative minimum tax and getting rid of the deduction for state and local taxes would hit higher-income families hard. The plan indicates Republicans would not change the progressivity of the current code, meaning that the rich would not get bigger cuts than the middle class and lower-income Americans.

As of now the “comprehensive report” and “powerful document” remains more of a series of guidelines, ones designed to give Republicans in Congress flexibility in writing the law and to give Republicans time to build support for the proposal before it becomes bogged down in fierce lobbying and bipartisan criticism. That means leaving a lot of tough questions—and basic questions—unanswered.