Republicans have suggested that the Internal Revenue Service may have intentionally lost years worth of e-mails to and from Lois Lerner, a central figure in the agency’s targeting controversy.

Congressional investigators have subpoenaed all of Lerner’s emails to determine whether politics motivated the IRS decision to screen nonprofit advocacy groups based on their names and policy positions. They also want to determine whether the White House was involved.

Below is a timeline to shed light on how the targeting and missing e-mail controversies evolved. Note: This is a living document that we plan to update as new information becomes available — we welcome input from readers.

March-April 2010 | IRS targeting begins 

The IRS experiences an increase in the number of applications for tax-exempt status from nonprofit advocacy groups after the Supreme Court’s Citizens United decision, which allowed corporations, unions and other organizations to spend unlimited funds on elections. The IRS begins searching for applications involving political sounding names, applying extra scrutiny to those organizations to determine whether they are following the rules for tax-exempt groups.

June 3, 2011 | GOP letter questions IRS about gift tax

House Ways and Means Committee Chairman Dave Camp (R-Mich.) issues a letter to the IRS questioning the agency’s decision to inform donors of nonprofit advocacy groups that their contributions might be subject to gift taxes. The letter does not mention targeting of conservative groups for extra scrutiny.

June 23, 2011 | Lerner hard-drive crash

Lerner’s hard drive crashes, causing her to lose e-mail files from 2009 through 2011.

Some Republicans have suggested that Lerner may have wiped out her e-mails because of Camp’s June 3, 2012 letter to the IRS. Fact Checker columnist Glenn Kessler awarded Three Pinocchios to that idea, noting that the letter dealt with gift taxes, not the targeting issue.

July 2011 | Lerner changes targeting criteria

Lerner in July 2011 discovers the use of inappropriate search terms that focus on group’s policy positions instead of their activities, according to an inspector general’s report. At that point, she orders her division to use more-generic screening criteria: “organizations involved with political, lobbying, or advocacy for exemption under 501(c)(3) or 501(c)(4).”

Her division eventually reverts back to using inappropriate methods.

August 2011 | E-mail recovery attempts failed

At this point, Lerner has sent her hard drive to the IRS’s IT department and Criminal Investigations division, where forensic experts tried to recover her files, according to internal e-mails. An IT manager told Lerner in August 2011 that the recovery attempts failed, according to the e-mails.

National Archivist David Ferriero testified Monday that the IRS should have informed the National Archives and Records Administration about the hard-drive problem. He said the agency “did not follow the law,” meaning it did not comply with the Federal Records Act.

June 2012 | Audit begins

Treasury Inspector General for Tax Administration begins an audit examining how IRS processes applications for tax-exempt status after Congress and news outlets report questionable treatment of conservative nonprofit groups.

May 10, 2013 | IRS apology

Lerner acknowledges that the IRS has targeted groups with “tea party” or “patriot” in their names. Her remarks came in response to a planted question at a legal conference.

May 13, 2013 | IRS targeting report

TIGTA releases a report on its audit, concluding that the IRS inappropriately selected nonprofit groups for extra scrutiny based on their names and policy positions.

February 2014 | IRS chief learns of missing e-mails

IRS Commissioner John Koskinen testified Monday that he first learned about a possible hard-drive problem in February 2014, but that the agency had not yet determined whether Lerner’s files could be recovered.

April 2014 | White House and Koskinen learn e-mails can’t be recovered

Koskinen learns that the IRS was unable to recover Lerner’s files and that the agency destroyed her hard drive years ago as a matter of protocol after attempts to retrieve the data failed. He said he does not recall who told him that the emails were unrecoverable.

The Treasury Department informs the White House that Lerner’s e-mails are lost before informing Congress about the matter. Koskinen denied during congressional testimony on Monday that he informed the White House about the issue, raising questions about who spread word to the West Wing.

June 13, 2014 | IRS tells Congress about missing e-mails

The IRS informs members of Congress that Lerner’s hard-drive crashed and that years worth of her e-mails are permanently missing, prompting a series of congressional hearings about the issue.

June 23, 2014 | Email probe

Koskinen acknowledges during a hearing with the House Oversight and Government Reform Committee that TIGTA is reviewing the missing e-mails and hard-drive crash.