The Treasury Department on Thursday introduced a plan to implement the Inflation Reduction Act's 15% corporate alternative minimum tax (CAMT) on companies with more than $1 billion in profit.

Treasury estimates about 100 of those companies would annually pay the CAMT. Without the CAMT, the department said in a statement, the companies would have a 2.6% effective federal tax rate, with 60% paying an effective federal tax rate of less than 1%.

Some 25% would have an effective tax rate of zero, according to the statement.

The companies' "ability to use complex strategies to avoid tax also gives them an unfair competitive advantage over small businesses, which don't have access to the same tax planning techniques and high-paid lawyers and accountants," Treasury said. "The CAMT helps level the playing field for small businesses by imposing a minimum tax on the profits that the largest corporations report to their shareholders."

Treasury said the rule change would implement the legal requirement that the companies pay at least 15% in taxes on profits they report to shareholders, with certain adjustments. The change would increase fairness and raise $250B over the next decade, with $20B coming in next year, the department added.

"The proposed rules released by Treasury today are an important step toward realizing Congress' efforts to address the most egregious U.S. corporate tax avoidance and ensure the largest and most profitable corporations in the country cannot pay little to no taxes," Treasury Secretary Janet Yellen said. "The Corporate Alternative Minimum Tax will also help level the playing field for small businesses while generating hundreds of billions of dollars in revenue."

The agencies said comments on the proposed rule changes will be accepted until Dec. 12, as well as requests to speak at a public hearing set for Jan. 16.