From ACLU:
Everyone knows the IRS is our nation’s tax collector, but it is also a law enforcement organization tasked with investigating criminal violations of the tax laws. New documents released to the ACLU under the Freedom of Information Act reveal that the IRS Criminal Tax Division has long taken the position that the IRS can read your emails without a warrant—a practice that one appeals court has said violates the Fourth Amendment (and we think most Americans would agree).
Last year, the ACLU sent a FOIA request to the IRS seeking records regarding whether it gets a warrant before reading people’s email, text messages and other private electronic communications. The IRS has now responded by sending us 247 pages of records describing the policies and practices of its criminal investigative arm when seeking the contents of emails and other electronic communications.
So does the IRS always get a warrant? Unfortunately, while the documents we have obtained do not answer this question point blank, they suggest otherwise. This question is too important for the IRS not to be completely forthright with the American public. The IRS should tell the public whether it always gets a warrant to access email and other private communications in the course of criminal investigations. And if the agency does not get a warrant, it should change its policy to always require one.