How the Billionaires Income Tax Would Work

WASHINGTON—Democrats are poised to consider a plan that would upend tax rules for the wealthiest Americans, as Senate Finance Committee Chairman Ron Wyden makes a late bid for a new capital-gains tax in President Biden’s social-spending and climate-change legislation.

Mr. Wyden’s detailed proposal—annual income taxes on about 700 billionaires’ unsold publicly traded assets such as stocks—arrives as Democrats are struggling to find up to $2 trillion over a decade to cover the cost of their agenda. They have plenty of ideas that would exceed that figure, but precious few that can muster the support of enough Democrats to get through the narrowly divided Congress.