If President Donald Trump does propose slashing the U.S. corporate tax rate to 15%, as reports have suggested, one estimate is that it could cost the government some $2 trillion in lost revenue.

Trump is preparing to roll out what he’s called a “big tax reform and tax reduction” package on Wednesday, and one of the details that has leaked out is cutting the corporate rate to 15% from 35%. Businesses and politicians regularly decry the 35% rate, though corporations often pay effectively less in taxes via deductions and credits.