WASHINGTON (Reuters) – U.S. President Joe Biden will propose a minimum tax on billionaires as part of the fiscal 2023 budget that is expected to be unveiled on Monday, a document released by the White House showed. Biden’s “Billionaire Minimum Income Tax” would set a 20% minimum tax rate on households worth more than $100 million, in a plan that would mostly target the United States’ more than 700 billionaires, according to a White House fact sheet released on Saturday. The plan would require such households to pay the minimum tax of 20% on all of their income including unrealized investment i…