Trump v. Mazars USA, LLP, 591 U.S. ___ (2020) was a landmark US Supreme Court case involving subpoenas issued by committees of the US House of Representatives to obtain the tax returns of President Donald Trump, who had litigated against his personal accounting firm to prevent this disclosure, although the committees had been cleared by the United States Court of Appeals for the District of Columbia Circuit.

It also noted that to request presidential documents like tax returns, Congress needs a legislative reason and may not conduct a criminal investigation, which is a power of the executive branch.

"[5] In April 2019, three committees of the US House of Representatives wanted to access the financial records of US President Donald Trump, his children, and affiliated businesses.

Although each of the committees sought overlapping sets of financial documents, all of them supplied different justifications for the requests and explained that the information would help guide legislative reform in areas ranging from money laundering and terrorism to foreign involvement in US elections.

In the United States Court of Appeals for the District of Columbia Circuit, on July 12, 2019, Trump said he was suing to prevent Mazars from complying with the subpoena and argued that the Committee's investigation into his financial records served no legitimate legislative purpose.

[9] On November 13, 2019, the DC Court of Appeals denied the Trump's petition for an en banc rehearing 7-3; Gregory Katsas, Neomi Rao, and Karen Henderson dissenting.

[8][11] House General Counsel Douglas Letter, in seeking a rapid subpoena ruling, wrote: "The President certainly has no right to dictate the timetable by which third parties provide information that could potentially be relevant to that inquiry.

[1] The question facing the Court was whether the US House of Representatives has the authority to issue subpoenas addressed to third parties to obtain the private financial records of the president and his businesses.

[25] In arguing against the need for subpoenas for tax returns, Deputy Solicitor General Jeffrey Wall repeatedly cited that they presented "dangers of harassing and distracting and undermining the President.

[28][27] Roberts wrote, "The standards proposed by the president and the solicitor general — if applied outside the context of privileged information — would risk seriously impeding Congress in carrying out its responsibilities....

The House's approach fails to take adequate account of the significant separation of powers issues raised by congressional subpoenas for the president's information.

Alito agreed that the case should be remanded but argued that the House committees had not shown adequate justification and that the majority opinion's criteria were an insufficient remedy for the lower courts.

While the challenges to the House subpoenas were returned to the Circuit Court for review based on the four considerations set out by Roberts, they were not resolved before the November 2020 presidential election.

[3] After Trump left office, on February 23, 2021, the House Oversight and Reform Committee in the 117th Congress reissued the subpoena to Mazars for the same documents it had previously sought.