The US' roughly 650 billionaires would have paid around $114 billion in 2020 under Warren's proposed "ultra-millionaire" tax, research suggests. : US billionaires would have paid $114 billion between them in 2020 under an "ultra-millionaire" tax proposed by Sen. Elizabeth Warren of Massachusetts on Monday, according to two tax groups. The bill, called the Ultra-Millionaire Tax Act, would apply an annual 2% tax on individuals with net worths between $50 million and $1 billion. Individuals worth more than $1 billion would pay an annual 3% tax if the bill becomes law.