WASHINGTON — A federal appeals court in Manhattan has rejected President Trump’s appeal to keep eight years of his tax returns secret.

The Monday ruling marks a significant loss for Trump, who has fought aggressively to keep his tax returns private, despite such disclosures being common practice among previous presidents.

Trump’s likely to appeal the ruling to the Supreme Court, in what promises to be a titanic Constitutional battle over the limits of presidential immunity from investigation and prosecution.

But for now, the ruling gives Manhattan District Attorney Cyrus Vance's subpoena for Trump’s financial records the legal imprimatur it needs to move forward.

“Any presidential immunity from state criminal process does not extend to investigative steps like the grand jury subpoena at issue here,” the three-judge panel wrote in its unanimous decision.

Vance subpoenaed Trump’s financial records and tax returns from his longtime accounting firm Mazars USA as part of an investigation into hush-money payments made prior to the 2016 election to women who claimed they slept with Trump.

Trump’s fight with Vance to keep his tax returns private is just one of the many courtroom battles the president is engaged in that could lead to bombshell revelations about the true scope of his business empire before the 2020 election — or drag out in endless litigation well past the vote.

In this particular case, however, Trump has staked out a position that outside lawyers call breathtaking in scope: That the president should be immune from both criminal prosecution and investigation, along with seemingly any individual or firm he has ever worked with, by extension.

The New York appeals court didn’t directly address that broader argument, which a lower court judge previously called “repugnant” to America’s “constitutional values.”

But on Monday, the New York appeals court ruled that whatever presidential shield of immunity Trump might have, it didn’t apply to his tax advisers.

“It is Mazars, not the President, that would be cited for contempt in the event of non‐compliance,” the judges wrote. “This case therefore presents no concerns about the constitutionality of holding a sitting President in contempt.”