Mnuchin had said on Tuesday that Treasury Department lawyers had held "informational" discussions with the White House about an expected request for the returns, a step that Democrats criticized as uncalled for under the law. Acting White House Chief of Staff Mick Mulvaney said Sunday that Democrats would never see them and the American public had already settled the politics of it when they elected Trump.
"It will be embarrassing if I keep this person waiting for a long period of time", Mnuchin said.
Ron Wyden, Democrat of OR, on a request made by House Ways and Means Chairman Richard Neal, Democrat of MA, who set a deadline of Wednesday for the submission of Mr. Trump's returns.
Mnuchin was an early Trump supporter and is one of the longest-serving members in the president's Cabinet.
"We would never ask for the White House's permission on this, " Mnuchin said.
The Ways and Means chair - known for a cautious temperament - tailored the letter for review by a judge during litigation that would follow the Trump administration's anticipated refusal, saying that the House needs the president's tax information - and the IRS's information on its processing of the president's taxes - to determine if he is being given an undue advantage thanks to his office.
That's the deadline they had given IRS Commissioner Charles Rettig to turn over six years of President Donald Trump's personal and business tax returns to House Ways and Means Chairman Richard Neal, a Massachusetts Democrat.
"There is no law, as you know, I got elected last time with the same issue and while I'm under audit, I won't do it".
Trump says he can not release the tax returns because he is under audit, and the administration has put up a united front aimed at blocking the documents from being released.
Mnuchin had been in the House Committee on Financial Services hearing that Waters was chairing for over three hours, but said he needed to leave at 5 p.m.to meet a senior official from the Bahraini government.
Neal, D-Mass., requested the returns last week in a letter to Mnuchin and set a deadline of Wednesday to provide them.
"You are instructing me to stay here and I am canceling my meeting" with the Bahraini official, Mnuchin said.
Federal law allows the Ways and Means and Senate Finance committees and the Joint Committee on Taxation to ask the IRS for the returns of any filer, but some legal scholars say a request requires Congress to have a legislative goal, including general oversight. "Voters knew the president could have given his tax returns. And I have the gavel", she said.
"Consistent with its authority, the Committee is considering legislative proposals and conducting oversight related to our Federal tax laws, including, but not limited to, the extent to which the IRS audits and enforces the Federal tax laws against a President", the letter reads.
"If this is the way you will treat me, I will rethink" returning, Mnuchin said at one point.
Mnuchin told Waters, "Please dismiss everybody". "You are ordering me to stay here". Or perhaps Mnuchin is just aiming to get fired so he can go back to making more millions and was treating Waters in a manner that would lead to that resolution post-haste.
Once again, Republicans are challenging rule of law and executive norms whenever possible, as presidents have been releasing their tax returns for decades.