The Senate has approved the most sweeping overhaul of the US tax code in more than 30 years.
Republicans cheered as the result of the 51-48 vote was announced.
The bill now goes to the House for a further vote later on Wednesday, with approval expected.
It would then go to President Donald Trump for his signature, enacting it into law.
The sweeping, $1.5tr (£1.1tr) tax bill marks a victory for the Republican Party and is the first major legislative victory for Mr Trump, who had long said he wanted to reform the country's tax system.
Measures included in the package include a cut to corporate income tax, from 35% to 21%, a 20% reduction on business income, cuts to the tax rate for highest earners and a change that means fewer people will pay inheritance tax.
The United States Senate just passed the biggest in history Tax Cut and Reform Bill. Terrible Individual Mandate (ObamaCare)Repealed. Goes to the House tomorrow morning for final vote. If approved, there will be a News Conference at The White House at approximately 1:00 P.M.
— Donald J. Trump (@realDonaldTrump) December 20, 2017
Democrats say that the legislation is a giveaway to corporations and the wealthy that will widen the gap between the rich and poor.
"It contains huge, permanent giveaways for big banks and corporations, and asks our children, millions of working Americans and senior citizens, and future generations to pay the price," Democratic Senator Chris Van Hollen said.
The Tax Policy Centre, a non partisan think-tank in Washington, has estimated that the bill will mean middle-income households see an average tax cut of $900 next year, while the wealthiest 1% of Americans will see their tax bill drop by $51,000.
The package also repeals parts of the Affordable Care Act, the measures known as Obamacare, and will allow drilling in Alaska's Arctic National Wildlife Refuge – amendments added to secure Republican votes in what was a narrow victory for Mr Trump.
No public hearings were held on the measure, and numerous amendments favoured by lobbyists were added.
Republicans back the bill as a boost to the economy that favours business and individuals in an economy they hope will grow faster.
"We've had two quarters in a row of 3% growth," Senate Republican leader Mitch McConnell said.
"The stock market is up. Optimism is high. Coupled with this tax reform, America is ready to start performing as it should have for a number of years."
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The tax cuts total nearly $1.5tr over the next decade – a sum to be added to the $20tr US national debt – and would take effect in January.
Workers would start to see changes in the amount of taxes withheld from their paychecks in February.