It's official: Trump Treasury Secretary Steven Mnuchin has written House Ways and Means chairman Richard Neal to tell him the administration will not be complying with the committee's request for Donald Trump's personal and business tax returns.
The anti-corruption law granting Congress the authority to access such records offers no exemptions, requiring Mnuchin to invent one—or rather, requiring Trump Attorney General William Barr to invent one.
In reliance on the advice of the Department of Justice, I have determined that the Committee's request lacks a legitimate legislative purpose, and pursuant to section 6103, the Department is therefore not authorized to disclose the requested returns and return information.
If it seems peculiar (and likely illegal) for Mnuchin and Barr to be blocking the release based on their own judgment that Congress lacks a "legitimate" purpose for asking for the sitting president's tax returns, it is. Mnuchin is correct in stating the committee's request is "unprecedented", however: Trump is the only modern president or candidate to refuse to make those tax records public.
Congress has ample reason to probe Trump's returns. In addition to determining just how Trump's new tax cuts have affected his own finances—a "legitimate" form of inquiry on its own—a New York Times examination of available Trump family documents revealed that Trump has engaged in "decades" of tax-dodging schemes, some of them likely criminal in nature.
Neal has acknowledged Mnuchin's letter, but is so far being terse in his public response: "I will consult with counsel and determine the appropriate response."
The move sets up a likely subpoena and court battle.
More significantly, it will escalate calls for the House to launch a formal impeachment inquiry into Trump. The courts have affirmed that Congress has especially broad powers to obtain documents for the purposes of impeachment; if the House were to move to impeach Trump, the administration would almost certainly be forced to release these and other documents, regardless of William Barr and Steven Mnuchin's own estimations of congressional "legitimacy."