Democrats, who oppose the controversial legislation, say Republicans "managed to take a bad bill and make it worse"
The largest overhaul in America's tax system for 31 years has been approved by the US Senate, in a crucial victory for Donald Trump.
US stock markets have rallied for months in the hope that Washington would provide major tax cuts for corporations and the narrow 51-49 vote in favour of the changes is set to result in a bill that will see the corporate tax rate slashed from 35% to 20%.
Analyses of the bill have shown wealthy Americans are likely to most significantly benefit, with The Washington Post suggesting the controversial reform offers "mixed blessings to everybody else".
The tax reductions for big businesses will see $1.4tn (€1.18bn) added to the $20tn national debt over the next 10 years, which the President and his fellow Republicans believe will boost an already growing economy.
The Senate and the House of Representatives - both controlled by the Republicans - are likely to begin talks over crafting a final bill next week, with Mr Trump - who promised tax reform during his election campaign - hoping to sign it into law by Christmas.
Following the vote, Mr Trump wrote on Twitter:
We are one step closer to delivering MASSIVE tax cuts for working families across America. Special thanks to @SenateMajLdr Mitch McConnell and Chairman @SenOrrinHatch for shepherding our bill through the Senate. Look forward to signing a final bill before Christmas! pic.twitter.com/gmWTny3SfS— Donald J. Trump (@realDonaldTrump) December 2, 2017
Republicans see the tax overhaul as crucial to their prospects in the mid-term elections in November 2018 - when they will have to defend their majorities in Congress - despite public protests against and polls showing little public enthusiasm for the measure.
Senate Majority Leader Mitch McConnell said: "Big bills are rarely popular. You remember how unpopular 'Obamacare' was when it passed?"
President Obama's healthcare law was in the firing line of the tax overhaul, with it taking steps to remove the mandate for all Americans to obtain health insurance or face a tax penalty - a policy designed to ensure a more viable health insurance market by forcing younger and healthier Americans to buy coverage.
Experts say millions of people stand to lose their health insurance because of the changes, but Republican Senator Bill Cassidy said: "Working families and middle-income families across the nation will be better off. Families who over the last eight years have not done well will begin to do better."
Republican Senator John McCain - who in July passed what looked to have been the decisive vote to keep the Affordable Care Act - was among those who voted in favour of the reform.
The only Republican dissenter was Senator Bob Corker, who joined the Senate's 48 Democrats & independents in voting against the overhaul as it stood to "deepen the debt burden on future generations".
Senate Democratic leader Chuck Schumer added: "The Republicans have managed to take a bad bill and make it worse. Under the cover of darkness and with the aid of haste, a flurry of last-minute changes will stuff even more money into the pockets of the wealthy and the biggest corporations."
Other opposition senators expressed frustration and anger over the process - saying they didn't even have enough time to read the version of the bill they were being asked to vote on.
I’m furious, but this fight is not over.— Sen. Cory Booker (@SenBooker) December 2, 2017
In the days and weeks to come, I’ll do everything I possibly can to ensure this embarrassment of a tax bill never becomes law.
I say to my Republican colleagues: The American people are catching on. While you may get away with this act of looting tonight, history is not on your side.— Bernie Sanders (@SenSanders) December 2, 2017
Okay this is absurd. One page of the new #GOPTaxPlan is crossed out with an ex. Another page is just a line. Is that a crossout? Is this page part of the bill?— Senator Bob Menendez (@SenatorMenendez) December 1, 2017
WHY AM I ASKING THESE QUESTIONS HOURS BEFORE WE VOTE ON IT?? #GOPTaxScam pic.twitter.com/57Qbi7gT5F