Two of the biggest pro-business groups in the country – the US. Chamber of Commerce and the Business Roundtable – are gearing up to fight new tax proposals in Congress as Democrats work to finish President Joe Biden’s social safety net and climate spending bill.

These proposals target billionaires via the tax code. They also propose a minimum 15% corporate tax on large corporation’s declared income.

Joe Manchin, a centrist Democrat has expressed some concern about the “billionaire tax”. As a senator from West Virginia and a key vote in Senate, he has worked hard to limit Biden’s proposal for the bill. But, he favors the minimum corporate income tax.

CNBC heard from the U.S. Chamber of Commerce – the largest business advocacy organization in the nation – that they are concerned about the speed with which lawmakers rush these proposed legislation through Congress.

“We are worried about the attempt to take down the 11^Th hour to rush through brand new, complex, and untested methods of taxation,” Neil Bradley, the group’s executive vice president and chief policy officer, said in a statement. He said that the group doesn’t think lawmakers have fully vetted their proposals in order to avoid unintended consequences.

Bradley explained that no lawmaker could claim to have taken into consideration the potential impact of such proposals.

A spokesperson for the Business Roundtable said that they oppose the minimum 15% corporate tax on large companies.

The spokesperson stated that the Business Roundtable would continue lobbying against tax hikes on America’s job-creators, such as the 15% “book minimum tax” currently under discussion. This group feels that the proposal will negatively impact tax incentives to encourage investment in equipment and plants, as well as the quality of financial reports.

The Business Roundtable includes Mary Barra, General Motors CEO, and Mary Barra from the Automobile Manufacturers Association. incoming chair of the lobbying group, Walmart CEO Doug McMillon. Jamie Dimon (CEO of J.P. Morgan Chase) and Tim Cook (CEO of Apple), are both members.

Democrats proposed new tax provisions to increase revenue for the spending bill.

The idea was introduced Tuesday by Democratic senators in the Senate. initiating a 15% minimum corporate tax on declared income of massive businesses, such as Amazon, Facebook and Tesla. Another option is to raise money via a billionaire tax, which would be used for unrealized gains. The tax would be applied to those who have more than $1 million in assets and incomes exceeding $100 million annually.

CNBC has reviewed lobbying disclosure records and found that the Chamber of Commerce as well as The Business Roundtable had already spent millions in lobbying Congress to address a variety of issues including tax reform and trade.

Both groups back President Joe Biden’s $1 trillion infrastructure bill, but they are opposed to the reconciliation package. Chamber of Commerce declared their continued opposition to the social-spending bill earlier this month In conclusion, the Business Roundtable stated in SeptemberIt was opposed to tax increases being included in the measure.

Over $16 Million was spent by the Chamber of Commerce lobbying Congress, Biden’s White House, and other components of his administration in the last quarter. Over the same period, the Business Roundtable spent more than $11 million lobbying Congress on related issues. It targeted congressional legislators and the Executive Office of the President as well as other parts of the Biden government.

These two giant lobbyists aren’t the only ones voicing concern about the proposed tax concept.

In a Twitter post, Elon Musk (CEO of Tesla) took aim at the tax on Monday. Forbes says Musk is the most powerful person in the world. a net worth of about $275 billion

CNBC interview: Ron Baron, billionaire investor and shareholder Ron Baron criticized Congress over their tax proposals. He also defended Musk’s new tax plans.

It feels as if Congress believes they’re Robin Hood from old times. Baron stated Wednesday that it felt like an Elon Musk tax bill. I don’t understand the vindictiveness shown against someone who does what he does. [Musk]Baron added that it had.

Forbes estimates that Baron’s net worth is more than $4Billion.