The Republican, known to be a billionaire himself, joked that he'd leave the United States to avoid paying the penalty but then said he'd "stick it out."
Democrats detailed their new tax proposal on Wednesday as a method to pay for President Joe Biden's Build Back Better plan. It was swiftly thwarted by bipartisan concerns and issues over the plan's constitutionality.
It's since been abandoned in favor of a surtax on wealthy Americans making more than $10 million.
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"What country will be the primary beneficiary from a 'Billionaires Tax,' or Wealth Tax? Where will wealthy people and companies move to, leaving the United States high and dry?" Trump said in an emailed statement.
"Most don't need to be in the U.S. anyway. I know all of those very smartly run countries, and they are all thrilled by what the Radical Left maniacs are doing in Congress.
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"I just wonder, will I be allowed to run for president again if I move to another country? No, I guess I'll just stick it out, but most others won't!"
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Senate Finance Committee Chairman Ron Wyden, D-Ore., published a bill called the "Billionaires Income Tax," which would tax capital gains on the unsold assets of billionaires such as stocks, and crucially affect some of the nation's wealthiest people like Amazon founder, Jeff Bezos, and Tesla CEO, Elon Musk. Musk, whose net worth is currently $287 billion per Bloomberg's real-time data on billionaires, signaled on Twitter that he opposes the proposal.
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"Eventually, they run out of other people's money and then they come for you," Musk wrote in response to a tweet featuring a templated letter opponents can send to their congressperson. The letter says that although holdings in 401(k) plans are excluded, the proposal takes tax hikes "a step closer to imposing unrealized capital gains tax on the average investor."
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However, as the richest man globally, Musk is far from the average investor and has seen his net worth rise by some $117 billion in 2021 alone, per Bloomberg's count.
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While the project has received support from the White House, critics call it unconstitutional, convoluted, or illegally targeting a specific group of people who have contributed to America's economic growth.
Wyden and proponents say it will guarantee the billionaires pay their fair share of taxes after reports that some of the richest 1% of Americans have legally avoided paying taxes on their wealth gains. This comes at a time of massive wealth inequality in the U.S. that experts have said is exacerbated by America's tax codes being tilted in favor of the wealthy.