We’re one day away from the formal introduction of a tax overhaul bill that will affect every taxpayer in America. On the eve of kickoff, though, almost nobody knows what’s in it. Even members of the House Ways and Means Committee, whose Republican chairman Kevin Brady is working on the bill, are in the dark. Last-minute additions and subtractions with enormous impact have been quietly announced, retracted, or kept up in the air.

The haphazardness calls into question whether congressional Republicans can accomplish the biggest rewrite of the tax code in 30 years—and get it done before Thanksgiving, as per the announced schedule. But it also guarantees that this bill, being patched together in a desperate lunge to offset revenue and please wary Republicans, will have massive and unexpected consequences for non-wealthy Americans.

All we know thus far about the bill comes from a two-page joint statement of principles from cabinet officials and congressional leaders in July, and a somewhat more detailed nine-page framework in late September. As the latter makes clear, Republicans want to cut taxes on the wealthy and corporations. As The New York Times reported at the time, “the president offered no measure of the plan’s cost and scant detail about how working people would benefit from a proposal that has explicit and substantial rewards for wealthy people and corporations.”

The plan significantly lowers individual income and corporate tax rates, while raising the standard deduction that all tax filers take (eliminating tax on the first $12,000 of individual income, $24,000 for a married couple). It creates a loophole on “pass-through” income for people who set up corporations, which could prove a major tax avoidance strategy. Another big loophole exempts foreign income earned by multinational corporations that have U.S. headquarters, creating huge incentives to designate as much “foreign” income as possible. And Republicans want to repeal the alternative minimum tax, which hits high-net worth individuals, and the estate tax, which affects wealthy scions.

These tax breaks for the rich are expensive—costing at least $3 trillion over the first ten years and $6.6 trillion afterward, according to the nonpartisan Tax Policy Center. Under the budget resolution passed last week, the tax plan is only allowed to create a maximum of $1.5 trillion in deficits over the first ten years and nothing thereafter, if Republicans use the budget reconciliation process. The debate over the final details of the bill is mostly about how Republicans will make up that difference.