Meta’s filings this week were dominated by a new class of nonvoting stock that would allow CEO Mark Zuckerberg to raise cash—potentially enough to cover a personal California wealth tax bill—without giving up control of the company. Meta says the new shares are needed to fund its AI ambitions: management forecasts “showed the Company’s need to raise hundreds of billions of dollars over a period of several years beginning as early as fall 2026,” according to its information statement.

While that disclosure relates to one individual’s potential tax bill, Meta’s quarterly report shows just how low the company’s own tax bill has become.

“Our effective tax rate for the nine months ended September 30, 2026 was 2%,” Meta said in the report, compared with the 21% statutory rate set in federal law. The company reported income before taxes of $53.5 billion for those nine months and a tax provision of $1.03 billion. Absent changes to its tax landscape, Meta added, “We expect our fourth-quarter 2026 tax rate to be between 15%–17%.”

An $8 Billion Treasury Break

Most of that gap traces to a single item. On Feb. 18, the Treasury Department issued Notice 2026-7, providing relief from the corporate alternative minimum tax related to previously capitalized U.S. research and development costs. Meta recognized an $8.03 billion tax benefit in the first quarter as a result, partially offsetting a $15.93 billion charge it recorded in the third quarter of 2025, once the One Big Beautiful Bill Act became law. That charge landed in a quarter when Meta’s effective tax rate was 87%.

The benefit has had an outsized effect on this year’s rate. Meta reported a first-quarter rate of negative 23%; without the Treasury benefit, it would have been 37 percentage points higher, or about 14%. Its first-quarter report says the rate fell “primarily due to Treasury Notice 2026-7.”

For the first nine months, Meta’s tax provision would have been about $9.06 billion without the benefit—roughly 17% of pretax income—according to a Fortune calculation based on its filings. Meta’s third-quarter rate, which the benefit did not affect, was 24%; the company says it would have been 17% excluding a $9.89 billion charge.

An Impending Deadline From Congress

Meta now faces an entirely different question about a different tax break from certain members of Congress. The company has drawn scrutiny for how it reportedly classified its data centers as experimental, which reportedly allowed Meta to receive the federal research and experimentation credit. Citing a New York Times report, Sens. Ron Wyden (D-Ore.), Sheldon Whitehouse (D-R.I.), Elizabeth Warren (D-Mass.), Catherine Cortez Masto (D-Nev.), Maggie Hassan (D-N.H.), Ben Ray Luján (D-N.M.), and Peter Welch (D-Vt.) wrote to Zuckerberg on Oct. 13, requesting an answer by Halloween about Meta’s federal tax filings.

The Treasury benefit and the research credit are separate parts of Meta’s tax picture. The former was recognized in Meta’s 2026 first-quarter accounts after the Treasury notice, while the senators’ questions concern the company’s treatment of data-center spending on federal tax filings from 2023 through 2025.

According to public records, the senators wrote, Meta claimed to the IRS on federal tax filings that its AI data centers are experimental “pilot models” that qualify for the credit. The letter says Meta has indicated in federal regulatory filings that it used the research credit to cut its federal income tax liability by $6.6 billion from 2023 through 2025: $700 million in 2023, $2 billion in 2024, and nearly $4 billion in 2025.

“The federal research credit can be a useful and necessary tool to support our nation’s innovation economy and cutting-edge research,” the senators wrote. “Subsidizing your A.I. data center build is not close to meeting this standard.” The letter asks Meta to say how much of its credit each year went to microchips, computing equipment, and other data center materials.

A Rainy Day Fund

Meta’s filings show how much of its tax savings remains open to question. Its gross unrecognized tax benefits—savings it has claimed but not yet counted as final—were $20.82 billion as of Sept. 30, up from $16.45 billion at the end of 2025. If they were realized in a future period, its tax provision would fall by $14.58 billion. The company says it expects to continue accruing them for certain recurring tax positions and believes its accrual is adequate. Meta’s annual report says the benefits were “primarily accrued for the uncertainties with our research tax credits and transfer pricing” with its foreign subsidiaries.

“AI companies are delivering a one-two punch to families, forcing Americans to subsidize their data centers with your tax dollars and higher utility bills,” Warren told Fortune. “We need to crack down on these Big Tech companies and make sure they pay their fair share.”

Meta defends its use of the credit. “Meta is one of the largest investors in research and development in the United States,” a Meta spokesperson told Fortune. “Over the last five years, Meta invested $200 billion in R&D—$57 billion in the last year alone, advancing frontier research, building new technology, and supporting American jobs.

“Unlike traditional data centers, AI-optimized data centers are inherently new and require extensive testing and experimentation that cannot be simulated in order to get the design and build right. This is precisely the kind of domestic investment Congress encouraged when it established these tax incentives decades ago.”

This story was originally featured on Fortune.com.