Some provisions are so vaguely written they leave experts scratching their heads, like a proposal to begin taxing the investment earnings of rich private universities’ endowments. The legislation H.R. 1 (115) doesn’t explain what’s considered an endowment, and some colleges have more than 1,000 accounts.

In many cases, Republicans are giving taxpayers little time to adjust to sometimes major changes in policy. An entirely new international tax regime, one experts are still trying to parse, would go into effect Jan. 1, only days after lawmakers hope to push the plan through Congress.

“The more you read, the more you go, ‘Holy crap, what’s this?’” said Greg Jenner, a former top tax official in George W. Bush’s Treasury Department. “We will be dealing with unintended consequences for months to come because the bill is moving too fast.”