The inquiry could eventually reveal if the administration failed to follow regular procedures after Congress requested the president's tax records.
The American public has seen personal tax information for every president from Nixon to Obama.
The lawsuit seeks to block a new New York law that allows Congress to obtain the president's state tax returns.
It's the latest escalation in the broader battle between Democrats and the Trump administration.
The New York State Senate passed a bill earlier this month with the hope of helping Congress obtain some of the president's tax returns.
by Alex Baumgart The Trump presidency is less than five months old, but has been a quick study at one longstanding D.C. tradition
The comedian said "it's time to fight for our country" at a New York rally demanding the president release his returns.
Sen. Susan Collins (R-Maine) told Maine Public Radio she would subpoena President Trump's taxes if necessary to find out if there are connections between the administration and Russia.
So long as Trump refuses to sell his vast business holdings (and that appears to be his plan, notwithstanding the constitutional violations that would create), these conflicts will be insoluble.
The statement follows a bombshell report that Trump could have not paid federal income taxes for 18 years.
"Ross hadn't cheated on Rachel yet."