Biden is again calling for a “billionaire minimum tax” in the state of the Union.

President Joe Biden will again call for a “billionaire minimum tax” in his State of the Union address on Tuesday.

Although details have not yet been released, Biden previously proposed a billionaire minimum tax in his 2023 federal budget, calling for a 20 percent levy on households with net worth greater than $100 million.

In the original plan, the 20% tax applied to “total income,” including regular income and so-called unrealized gains or investment growth, according to the US Treasury Department sketched.

“This minimum tax would ensure that the wealthiest Americans no longer pay a lower tax rate than teachers and firefighters,” the White House said in a statement press release On Monday, the average federal income tax rate for billionaires is typical around 8%.

However, Biden’s original billionaire minimum tax didn’t gain traction in Congress, and it’s now even less likely to happen with a Republican-controlled House, experts say.

“I view this billionaires’ minimum income tax as a draft message to highlight some of the issues with our tax code,” said Steve Rosenthal, senior fellow at the Urban-Brookings Tax Policy Center.

Senate Democrats pushed for a similar billionaire tax in October 2021 to fund their spending agenda domestically. But the plan never gained broad support within the party.

“I don’t see much support for Biden’s billionaire minimum tax up the hill,” Rosenthal said.

The tax foundation also has concerns expressed over Biden’s original proposal, arguing that the plan adds “new compliance and administrative challenges to an already overburdened IRS.”

The Senate version of the billionaire minimum tax has also raised legal questions, with experts questioning whether unrealized gains count as income taxable under the 16th Amendment.

There are also debates about the definition of “billionaire” and the politics’ wealth calculation. Experts say if it’direct tax‘, it has to be split into states based on population, which isn’t possible because some places don’t have billionaires.

“I would characterize the landscape here as a lot of uncertainty about whether or not this would pass the constitutional muster,” Garrett Watson, senior policy analyst at the Tax Foundation, previously told CNBC.

However, Senate Finance Committee Chairman Ron Wyden, D-Ore., insisted their plan was constitutional because it provided for “annual taxation of income from capital gains” — a concept already part of the tax code.