As the U.S. Department of the Treasury works on final rules for a corporate alternative minimum tax for corporations that earn $1 billion or more per year, the large companies affected by the provision in the Inflation Reduction Act enabling that tax are lobbying Treasury to be more lenient toward them, The Washington Post reported.

Treasury issued its initial guidance regarding the application of the 15 percent corporate minimum tax last year. The final rules will set the terms for how companies should determine their income, and more broadly, which policies in the corporate tax code should apply to the new system.

“We value stakeholder input as we’ve worked on this project but we keep as our north star congressional intent, which is the idea of making sure we make the tax code more fair,” Deputy Treasury Secretary Wally Adeyemo told the Post.

In the absence of final rules, the IRS announced in June that it does not expect companies to begin estimating and paying the new tax yet on a quarterly basis and would not penalize those that did not pay.

Estimates vary as to how much the minimum tax would raise. The nonpartisan Joint Committee on Taxation estimated last year that about 150 corporate taxpayers could be forced to pay the new tax, later finding it could generate more than $222 billion in federal revenue over the next decade. But the haste with which the law was written may complicate who pays—and how much.

Companies such as AT&T, Amazon, Duke Energy, Ford and FedEx, among others, have mobilized to lobby Treasury to make changes that would reduce the taxes they owe under the law. Lobbyists for gas companies warned they could raise prices on customers depending on how the administration implemented the tax rules.

“These lobbies exist not to create clarity in the tax law, but to reduce the tax liability of the companies they represent,” Matt Gardner, a senior fellow at the Institute on Taxation and Economic Policy, told the Post.

“There are virtues to the [corporate alternative minimum tax], but I don’t think anyone thinks with a straight face thinks that simplicity is one of them,” said Chye-Ching Huang, the executive director of the Tax Law Center at the NYU School of Law. “It’s a lot of decisions Congress has left to Treasury and the IRS to figure out in some of the hardest areas.”

In negotiating its way to a final agreement, Congress agreed to shield entire industries from the new tax. In one example, Sen. Kyrsten Sinema (I-Ariz.), pushed to protect private equity as a requirement for her vote, the Post reported.

The lobbyists targeting Treasury are arguing for a lenient hand by suggesting that that tax would threaten economic growth. “There are reasons and incentives that Congress gave businesses to do certain good things in the economy,” Lara Muldoon, the senior director for government affairs at the Information Technology Industry Council, a trade group that represents Amazon, Facebook, Google and other technology giants, told the Post.

Treasury representatives have argued that the minimum tax contributes to a more equitable tax system. “By ensuring large, profitable companies and high-income individuals pay their fair share through these provisions and others, we are making our tax system and economy work better for everyday Americans,” said Lily Batchelder, the assistant treasury secretary for tax policy, in a speech in San Diego earlier this year.

The Treasury is expected to issue its rules by the end of the year, according to experts interviewed by the Post.