How Democrats Would Tax Billionaires to Pay for Their Agenda

The plan stakes out new territory by putting levies on unrealized gains in the value of billionaires’ liquid assets, such as stocks, bonds and cash.

WASHINGTON — Senate Democrats plan to tax the richest of the rich, hoping to extract hundreds of billions of dollars from the mountains of wealth that billionaires sit on to help pay for their social safety net and climate change policies.

The billionaires tax would almost certainly face court challenges, but given the blockade on more conventional tax rate increases imposed by Senator Kyrsten Sinema of Arizona, Democrats have few other options for financing their domestic agenda.

It would for the first time tax billionaires on the unrealized gains in the value of their liquid assets, such as stocks, bonds and cash, which can grow for years as vast capital stores that can be borrowed off to live virtually income tax free.