From the Washington Post:  

The IRS shared the full scope of its backlog with the House Ways and Means Committee and the agency’s own government watchdogs. The numbers, obtained by The Washington Post, dwarf the data the IRS has shared with the public. The IRS communicated its plans to adjust the tax-filing deadline to House and Senate lawmakers on Wednesday, although the agency briefly stoked confusion about the exact date of the change.

(Translation:  Wait till tomorrow's hearing, when the excrement hits the ventilator)