(CNN)Here's some background information about the Internal Revenue Service (IRS) scandal involving the targeting of certain groups. In May 2013, the Treasury Inspector General for Tax Administration released a report indicating the targeting involved delaying the processing of applications by certain conservative groups and requesting information from them that was later deemed unnecessary.
The Justice Department is investigating circumstances surrounding the disappearance of IRS emails that Republicans believe could shed light on the possible targeting of conservative and other political groups by the agency.
The investigation into the email disappearance, which the IRS said was due to a crash of former IRS official Lois Lerner's hard drive, is part of a wider criminal probe of whether any IRS employees broke the law in unfairly singling out specific political groups for extra scrutiny.
296 applications by groups were flagged for further review. About 75 groups had names with "tea party" or "patriot" in them.
Early 2010 - According to the May 2013 Inspector General report, "Inappropriate Criteria Were Used to Identify Tax-Exempt Applications for Review," the inappropriate targeting of mainly conservative groups begins. This targeting involves delaying the processing of their applications and requesting information deemed unnecessary.
May 2010 - According to the report, "EO function officials stated that, in May 2010, the Determinations Unit began developing a spreadsheet that would become known as the "Be On the Look Out" listing (hereafter referred to as the BOLO listing) "which included the emerging issue of Tea Party applications."
July 2010 - The Determinations Unit managements asks its specialists to BOLO for Tea Party applications.
2010-2012 - According to the report, action is taken to change the criteria used "for identifying potential political cases" involving groups seeking tax-exempt status approximately five times over a two-year period.
May 2012 - After the IRS is first notified of the practice, the use of some BOLO lists involving conservative labels is stopped.
May 10, 2013 - Miller helps engineer an apology by Lois Lerner, the director of the Exempt Organizations Division since January 2006, through a planted question at an American Bar Association meeting.
-- The IRS holds a conference call with reporters where they admits they've made "mistakes" in the last few years while trying to process requests from groups seeking tax-exempt status.
May 16, 2013 - President Obama chooses a new acting commissioner, Daniel Werfel, who had been the controller of the White House's Office of Management and Budget.
May 22, 2013 - Lerner invokes her Fifth Amendment right against self-incrimination after she denies any wrongdoing in a brief statement to the House Oversight Committee. It is later determined she waived these rights.
-- Douglas Shulman denies he knew about the targeting, and when he found out about some of it, he made steps to have it reviewed.
-- Steven Miller claims the targeting happened because of being staffers being overworked and not understanding unclear regulations rather than because of political motivations.
May 23, 2013 - After Lerner refuses to resign, she is placed on administrative leave, according to Congressional sources in both parties.
June 12, 2013 - Werfel stops the use of all BOLO lists by the tax-exemption unit after learning that some of them were still in use.
June 24, 2013 - Democratic Congressman Sander Levin of Michigan charges that liberal groups were targeted by the IRS as well.
September 23, 2013 - Lois Lerner retires.
December 20, 2013 - John Koskinen is appointed to the IRS commissioner position.
March 5, 2014 - Lerner refuses to testify before the House Oversight and Government Reform Committee.
March 26, 2014 - Koskinen testifies before the House Oversight and Government Reform Committee about how the IRS is going to try and restore public trust when it comes to exempt organizations.
April 10, 2014 - The Republican-led House Oversight Committee votes 21-12 to charge Lerner with contempt of Congress.
May 7, 2014 - Lerner is held in contempt of Congress by the House.
June 13, 2014 - IRS informs congress that it is unable to recover Lerner's e-mails from January 2009 to April 2011 because of a computer crash. The emails were subpoenaed by the House Oversight Committee Chairman. They have subsequently been able to recover 24,000 of the e-mails.
December 23, 2014 - The sixth report from the House Oversight Committee says that the IRS "systematically targeted" conservative groups, and places blame on Lerner and seven other IRS officials. According to the report, "The fact-finding is not yet complete." Another 30,000 e-mails to and from Lerner have been recently recovered which will also be looked at.
March 31, 2015 - The U.S. Attorney's Office sends a letter to House Speaker John Boehner notifying him that it won't bring contempt of Congress charges against Lois Lerner.