Since former IRS official Lois Lerner in May 2013 publicly admitted that the federal agency inappropriately targeted certain political groups, investigators and members of Congress have tried to get to the bottom of the scandal. The controversy has evolved over the months, with new revelations keeping alive conservative suspicions that the IRS has served as a political tool for the Obama administration.
Here are four things to keep in mind at this point in the investigations:
1. There's no evidence of White House involvement at this point
So far, six investigations (four led by congressional committees, one by the Justice Department and one by the Treasury Inspector General for Tax Administration) have not produced any evidence that the inappropriate activity at the IRS was prompted by the White House.
Days after Lerner blew the lid off the scandal, the Treasury Inspector General (TIGTA) issued a report into the misconduct. TIGTA began its investigation in July 2012. J. Russell George, the inspector general for tax administration, told the House Ways and Means Committee that the TIGTA review produced no evidence of political motivation behind the selection of which groups to target.
Additionally, Rep. Elijah Cummings, D-Md., the top Democrat on the House Oversight Committee, has pointed out that after interviewing 41 people about the misconduct, the Oversight Committee staff has produced no connection to the White House.
Meanwhile, House Ways and Means Committee Chairman Dave Camp, R-Mich., requested Lerner's emails to and from the White House from 2009-2011, but White House spokesman Jay Carney said earlier this month that there were "zero emails" between Lerner and anyone within the Executive Office of the President during that period.
2. Missing Lerner emails are keeping suspicions alive
Conservatives are insisting that a lack of evidence doesn't prove the White House wasn't involved. In fact, the fact that the IRS is incapable of producing some of Lerner's past emails suggests, as Camp put it, that there may have been "nefarious conduct that went much higher than Lois Lerner."
Earlier this month, the IRS revealed that it couldn't produce all of the emails because Lerner's computer crashed in 2011 and IT technicians could not restore her hard drive. Republicans are now intent on finding those emails.
Texas Republican Reps. Louie Gohmert and Bill Flores introduced legislation this week that would award $1 million to anyone who can recover the lost Lerner emails and $500,000 for information that could be used to prosecute anyone for the destruction of the emails.
"It seems that each time the IRS has evidence that will either prove with certainty its guilt or innocence, the evidence disappears, which both common sense and the law indicate the evidence such as emails must have proved the IRS's impropriety if not outright crimes," Gohmert said in astatement.
The new IRS commissioner John Koskinen said on CNN Thursday that he expects an independent investigator to produce a report on the missing emails within the coming weeks. "I think the appropriate way to proceed is, let's see what the IG finds out," he said.
Meanwhile, House Oversight Committee Chairman Darrell Issa, R-Calif., has issued a subpoena to the head of the Federal Election Commission (FEC), asking for all of Lerner's emails dating as far back as 1986. Lerner worked for the FEC from 1981 through 2001.
3. Republicans want what they'll never get: a special prosecutor
Republicans in Congress say that in the wake of the revelations about the missing emails, the Justice Department must fund an independent special prosecutor to investigate the whole scandal. However, the administration is against the idea.
Koskinen, citing the multiple other investigations into the controversy, said it would be "a monumental waste of taxpayer funds."
White House spokesman Josh Earnest earlier this month rejected the idea because "even the politically motivated investigation has not turned up any facts that support the conspiracy theories that [Republicans have] propounded."
"The fact of the matter is after 13 months of multiple congressional investigations, including 14 congressional hearings, 30 interviews with IRS employees, 50 written congressional requests, and as I mentioned 750,000 pages of documents, there is zero evidence to support Republican claims," he said. "And that's even -- again, these are investigations that have a pretty transparent political motive. So I'm not sure that there's a whole lot more to be discovered here."
Nevertheless, Sen. Ted Cruz, R-Texas, has charged that Attorney General Eric Holder should be impeached if he doesn't appoint a special prosecutor.
4. The IRS still working on getting to the root of the problem
Amid all the outside investigations looking into the IRS's past misconduct, the agency is still attempting to rewrite its rules to make sure it knows how to appropriately deal with tax-exempt nonprofits in the future.
Currently, "social welfare" organizations, which fall under the 501(c)4 classification, are allowed to spend unlimited sums of money on politics as long as politics isn't their main focus. These tax-exempt organizations are not required to disclose their donors -- so after the Citizens United Supreme Court case in 2010 cleared the way for corporations to spend unlimited amounts of money in politics, the number of applications for 501(c)4 status more than doubled.
Democrats argue that the IRS inappropriately targeted some of these groups because they have not been well-regulated. Nonpartisan groups like the ACLU have called on the IRS to adopt a "bright-line standard" that would give guidance on the sort of political activity that these groups can engage in.
The IRS last year put out proposed rule changes that would have limited the "candidate-related political activity" that these groups can conduct, but liberals and conservatives alike objected to the proposed changes. Last month, the agency said it would take another stab at rewriting its rules.