The Republican-controlled U.S. House of Representatives approved sweeping, debt-financed tax legislation on Tuesday, sending the bill to the Senate, where lawmakers were due to take up the package later in the evening.

The biggest overhaul of the U.S. tax system in more than 30 years could be signed into law by President Donald Trump as soon as Wednesday, if both chambers of Congress approve it.

The bill passed the House by a vote of 227-203, overcoming united opposition from Democrats and 12 Republicans who voted against it.

Passage was all but certain in the Republican-controlled Senate, as well.

The plan includes steep tax cuts for corporations and wealthy taxpayers, as well as temporary tax cuts for some individuals and families. It repeals a section of the Obamacare health system and allows oil drilling in Alaska’s Arctic National Wildlife Refuge, just two of many narrow changes added onto the bill to secure sufficient to win its passage.

Middle-income households would see an average tax cut of $900 next year, while the wealthiest 1 percent of Americans would see an average cut of $51,000, according to the nonpartisan Tax Policy Center, a think tank in Washington.

Republicans insist the package will boost the economy and job growth. They also see the measure as key to retaining their majorities in the House and Senate in elections next November.