The IRS memo demolished Mnuchin's arguments for denying the request for Trump's taxes by Ways and Means committee chair Rep. Richard Neal (D-MA).
In a letter sent just before the 5 p.m. deadline, Mnuchin made the unsubstantiated claim that Rep. Neal's request "lacks a legitimate legislative purpose."
The House Ways and Means Committee late Friday subpoenaed both Mnuchin and IRS Commissioner Charles Rettig for Trump's taxes.
The Ways and Means committee could issue a subpoena for Trump's taxes, or sue the Treasury Department to force Mnuchin to hand them over.
While trying to defend Trump, Grassley made a key mistake: He told the truth -- and made the case for why the country should see Trump's secret taxes.
Beyond Trump's personal tax returns, Rep. Richard Neal (D-MA) is requesting the returns of Trump's trust and seven Trump business entities.