WASHINGTON, D.C.: The Internal Revenue Service mistakenly shared the taxpayer information of thousands of people with the Department of Homeland Security under a controversial immigration data-sharing agreement, according to a court filing.

The disclosure concerns an agreement signed last April between Treasury Secretary Scott Bessent and Homeland Security Secretary Kristi Noem. The deal allows U.S. Immigration and Customs Enforcement to submit names and addresses of immigrants in the country illegally to the IRS for cross-checking against tax records.

A declaration filed this week by IRS Chief Risk and Control Officer Dottie Romo said the agency was able to verify only about 47,000 of the 1.28 million names ICE requested.

For fewer than five percent of those individuals, the IRS provided ICE with additional address information, potentially violating privacy protections designed to safeguard taxpayer data.

Romo said Treasury informed DHS in January about the mistake and asked the department to help "promptly taking steps to remediate the matter consistent with federal law," including "appropriate disposal of any data provided to ICE by IRS based on incomplete or insufficient address information."

The IRS-DHS agreement has faced legal challenges since its announcement. Public Citizen sued the Secretaries of the Treasury and Homeland Security, along with their agencies, on behalf of immigrant rights groups shortly after the agreement was signed.

A federal court in Massachusetts recently ordered the IRS to stop sharing residential addresses with ICE. In November, another federal court blocked the IRS from sharing information with DHS, ruling that the agency had illegally disseminated some migrants' tax data last summer.

The erroneous disclosure was first reported by The Washington Post. An IRS spokesperson did not respond to a request for comment from The Associated Press.

Advocacy groups say the potential unlawful release of taxpayer records raises serious privacy concerns and could have harmful consequences.

Lisa Gilbert, co-president of Public Citizen, said, "This breach of confidential information was part of the reason we filed our lawsuit in the first place. Sharing this private taxpayer data creates chaos and, as we've seen this past year, if federal agents use this private information to track down individuals, it can endanger lives."

Tom Bowman, policy counsel for the Center for Democracy & Technology, said that "the improper sharing of taxpayer data is unsafe, unlawful, and subject to serious criminal penalties."

"Once taxpayer data is opened to immigration enforcement, mistakes are inevitable, and the consequences fall on innocent people," Bowman said. "The disclosure of thousands of confidential records, unfortunately, shows precisely why strict legal firewalls exist and have — until now — been treated as an important guardrail."