In public, in Washington, there’s a raucous and freewheeling fight over tax policy. It pits Republicans against Democrats, and it’s battled out on the floor of the House and before the cameras of cable news shows.

But in private, there’s a parallel conflict that’s closely linked to Congress’ public tax wranglings. It pits a hedge fund owned by one of the president’s most powerful backers against the IRS. It’s a battle for $7 billion. And it’s so secretive that the hedge fund might have already won.

On July 21, 2014, the Senate Permanent Subcommittee on Investigations issued a bipartisan report accusing Renaissance Technologies, the country’s most profitable hedge fund, of misusing a financial tool to dodge taxes. The company had been using a banking method called “basket options” to trim upward of $6.8 billion off its tax bill, according to that report from Sens. Carl Levin (now retired) and John McCain.

A spokesman for Renaissance Technologies—whose co-CEO is billionaire Trump backer Bob Mercer—said the hedge fund politely disagreed with the committee, indicating it would not be paying up.

Almost exactly a year later—July 27, 2015—the IRS released a bulletin indicating that it believed using the basket option banking strategy the way hedge funds like Renaissance Technologies had been was unlawful.

That report did not mention Renaissance Technologies. But the battle lines were clear.

McClatchy reported in May of this year that the IRS was “demanding” that the hedge fund pay more than $7 billion in back taxes.

Sources familiar with the IRS’ inner workings told The Daily Beast that one likely potential resolution to this conflict would be a settlement; the IRS and the hedge fund could potentially make a deal to make the problem go away. And it’s possible that they’ve made such a deal already, according to Martin Sheil, a former criminal investigative agent for the IRS.

Federal law would bar the IRS from sharing information about such a settlement with the public—even though it involves billions of would-be tax dollars—and the hedge fund’s managers would likely see little benefit in releasing information on the matter.

If the fund and the IRS can’t make a deal—and their public statements indicate neither party is willing to yield on the basket options question—then Renaissance Technologies could take its tax battle to the United States Tax Court, which has public proceedings. The court’s docket currently indicates that it doesn’t have proceedings underway regarding the fund.

“The issue Renaissance Technologies is going to look at is, ‘Do we really want to argue in front of a judge, who’s the sole arbiter, who really understands taxes?’” Sheil said. “It’s going to be very transparent, very quickly, that these basket options are just baloney.”

“Renaissance Technologies probably knows that they’re going to lose,” he added. “Certainly, if they go into Tax Court, they’re going to lose.”

In the meantime, the Capitol Hill tax battle could be the Mercers’ saving grace.

“All it would take is a tweak of the tax code to say that what they are doing is now legal,” said a former prosecutor from the Justice Department’s tax division, who spoke anonymously to be frank about federal law enforcement and tax law.

“With those kind of connections, maybe you don’t have to do any lobbying,” he added.

The Mercers’ connections to Trump World are deep and wide. They generously funded a super PAC that boosted his campaign and have had numerous joint conservative activism endeavors with Steve Bannon—some of which have drawn criticism from transparency advocates.

Kellyanne Conway, now a senior White House official, wore a Superwoman costume to the Mercers’ lavish holiday party in December and tweeted a photo of herself there with then-President-elect Trump. The Daily Beast spotted Rebekah Mercer in a seat of honor on the Capitol steps for his inauguration.

The Mercers don’t need to make friends in the White House. They already have plenty there.

Still, tax reform is hard. And sources knowledgeable about the IRS’ inner workings told The Daily Beast that the much more likely outcome would be a settlement between the IRS and the hedge fund. Sources said these settlements resolve the vast majority of disputes over tax bills.

Any settlement would involve billions of dollars and likely require some sort of approval from the IRS commissioner and the agency’s chief counsel—the two positions there that require Senate confirmation—per sources familiar with these kinds of matters.

And that could mean a missed opportunity for the Mercers.

“They can’t anticipate any favoritism from all their hard work and donations to the campaign, which most people would view as a good thing,” the former federal prosecutor said, noting that career officials will likely be running the IRS for the foreseeable future. “If they were hoping to have any influence on a settlement with the IRS, that opportunity has come and gone.”