The Treasury Department must turn over six years of former President Donald J. Trump’s tax returns to House investigators, the Justice Department said in a legal opinion issued on Friday that potentially paves the way for their eventual release to Congress and to the public.
The 39-page opinion from the Justice Department’s Office of Legal Counsel dealt a sharp legal blow to a yearslong campaign by Mr. Trump to keep his tax information secret, reversing a Trump administration position that had shielded the documents from Congress. Rejecting that view, the Biden administration opinion said that a request for the tax information first lodged in 2019 by the House Ways and Means Committee was legitimate and that the Treasury Department had no valid grounds to refuse it.
“The chairman of the House Ways and Means Committee has invoked sufficient reasons for requesting the former president’s tax information,” the opinion said. “Treasury must furnish the information to the committee.”
Democrats on Capitol Hill, who said they were examining the Internal Revenue Service’s presidential audit program and Mr. Trump’s conflicts of interest, hailed the decision as a victory for congressional oversight powers and for national security. The House had sued to enforce the request after the Trump Treasury Department objected and litigation remains ongoing.
“The American people deserve to know the facts of his troubling conflicts of interest and undermining of our security and democracy as president,” Speaker Nancy Pelosi said in a statement.
Still, the matter remains far from settled. Biden administration officials said that the Treasury Department intended to comply with the legal opinion and would soon inform the courts that it had reached an agreement to hand the documents over to the House — lowering a key barrier. But Mr. Trump could still take legal action to try to get a judge in the case to block their transfer. That could take months or longer to work out.
Nor does the development necessarily mean that Mr. Trump’s tax information would immediately become public. Rules governing the sharing of sensitive tax information with the Ways and Means Committee require the panel to hold formal votes if it wants to share any of the information with the broader House or the public, or even include it in a committee report released to the public.
“As I have maintained for years, the committee’s case is very strong and the law is on our side,” Representative Richard E. Neal, Democrat of Massachusetts and chairman of the Ways and Means Committee, said in a statement. “I am glad that the Department of Justice agrees and that we can move forward.”
Mr. Trump’s personal lawyer Ronald Fischetti did not immediately return phone calls and emails seeking comment on Friday. Reached by phone, Phyllis A. Malgieri, Mr. Fischetti’s legal partner, said, “Knowing him for 32 years, the Italian in him, I’m sure he would have something to say” about the decision. Mr. Trump’s spokeswoman did not immediately return a request for comment.
Republicans on Capitol Hill quickly derided the decision as “politically motivated.” They warned that it could usher in a new era of political warfare in which politicians rifled through the tax information of their political enemies.
“If politicians in Congress can demand, and ultimately make public, the president’s private tax returns, what stops them from doing the same to others they view as a political enemy?” said Representative Kevin Brady of Texas, the top Republican on the House tax-writing committee.
In fact, though, Mr. Trump was an outlier in his refusal to publicly release the tax documents as a candidate or as president.
The determination by the Justice Department came more than a year after the Supreme Court ruled that Mr. Trump’s tax returns must be shared with the Manhattan district attorney’s office, which had sought them as part of a criminal investigation into the Trump Organization.
Last year, The New York Times obtained and analyzed decades worth of tax information for Mr. Trump and his companies that showed the former president had gone years without paying federal income taxes and reported hundreds of millions of dollars in business losses. But the information sought by the House would likely provide a more comprehensive window into his complex financial dealings.