Treasury Secretary Steven Mnuchin (shown) told House Ways and Means Chairman Richard Neal Neal on the first deadline that the Treasury was consulting with the Justice Department on turning over President Donald Trump’s tax returns.
Credit: Alex Wong/Getty

Treasury Secretary Steven Mnuchin left little doubt Tuesday that the administration will reject a congressional request for President Donald Trump’s tax returns by a self-imposed May 6 target for a “final decision,” setting the stage for a legal battle that will test the limits of congressional oversight.

In a 10-page letter to House Ways and Means Chairman Richard Neal (D-Mass.), who formally requested Trump’s returns on April 3, Mnuchin questioned Neal’s motives and laid out “some of the legal concerns” the administration has with the request. While Neal has argued that the committee needs to see the returns as part of its oversight of the IRS, Mnuchin wrote that is a “pretext” for the Democrats’ aim to make Trump’s returns public, which Mnuchin called “constitutionally suspect.”

Neal, who had set a 5 p.m. […]