A look at events leading to the disclosure that the Internal Revenue Service placed conservative groups under special scrutiny for 18 months before the 2012 elections, a practice that has prompted congressional inquiries, a Justice Department criminal investigation and the ouster of the agency's acting chief:
March-April: IRS agents begin giving extra attention to tax-exempt applications from groups associated with the tea party or with a political sounding agenda in their names, such as "Patriots," ''Take Back the Country" or "We the People," according to the IRS inspector general.
August: The first IRS "BOLO" listing — meaning Be on the Lookout — is issued for "various local organizations in the Tea Party movement" that are seeking tax-exempt status.
June: Lawmakers send the first of at least eight letters asking the IRS to address complaints that conservative groups are being subjected to burdensome screening in their applications for tax-exempt status.
June 29: Lois G. Lerner, in charge of overseeing tax-exempt organizations at the IRS, learns at a meeting that groups are being targeted, according to the inspector general. Lerner is told that groups with "Tea Party," ''Patriot" or "9/12 Project" in their names were being red-flagged. Statements in case files that are critical of the country's leadership or that want to "make America a better place to live" also prompt examination. Lerner directs agents to change the criteria for flagging groups immediately, the inspector general says.
Dec. 16: Despite being briefed about the matter six months earlier, Lerner does not divulge the flagging of conservative groups when she and others from the IRS meet staff members of the House Ways and Means Committee to discuss the issue, according to the staff's timeline of events.
January: The criteria for screening, altered after Lerner's staff meeting six months earlier, is modified again. Now the IRS is on the lookout for references to the Constitution or Bill of Rights in the materials of organizations seeking tax-exempt status, for "political action type organizations involved in limiting/expanding government," and more.
March 22: IRS Commissioner Douglas Shulman tells Congress there is "absolutely no targeting" of groups based on their political views.
May: Lerner does not divulge the flagging in 45-page letters to two lawmakers inquiring about the issue.
May 3: Deputy Commissioner Steven T. Miller is told by staff that that applications for tax-exempt status by tea party groups were inappropriately singled out for extra scrutiny, according to the agency. (Miller later becomes acting commissioner.)
June 15: Miller responds to a letter from Rep. Charles Boustany, R-La., who had raised concerns about possible harassment of tea party groups by the IRS. Miller does not concede conservatives had been singled out. He says generally that the IRS is seeing more tax-exempt applications from politically active groups and taking steps to "coordinate the handling of the case to ensure consistency."
July 25: Miller testifies to the House Ways and Means oversight subcommittee but does not divulge what he was told in May about the screening of tea party groups.
Sept. 11: Millers writes a letter responding to Utah Sen. Orrin Hatch, the top Republican on the Senate Finance Committee but again does not own up to the scrutiny conservatives were placed under. Hatch had written three times to the IRS about the complaints.
Nov. 6: The presidential and congressional elections.
Nov. 15: Lerner and others from the IRS meet Ways and Means staff but again do not acknowledge the targeting.
Week of April 22: White House counsel learns that the inspector general is finishing a report about the IRS office in Cincinnati, which handles tax-exempt applications, according to White House spokesman Jay Carney.
May 10: Lerner apologizes on behalf of the IRS for "inappropriate" targeting of conservatives; White House counsel is said to receive inspector general's report; President Barack Obama is said to have heard of the matter for the first time. Lerner says no high-level officials were aware of the targeting, a statement seemingly at odds with the timeline of events, and blamed low-level employees in Cincinnati.
May 13: Obama says if the IRS intentionally went after conservatives, that's "outrageous." The Democratic-controlled Senate Finance Committee joins Republican-led House committees in planning fresh investigations of the matter.
May 14: Miller says his agency demonstrated "a lack of sensitivity" in trying to figure out whether organizations claiming a tax exemption met the standard for it. The Justice Department says it will conduct a criminal investigation, the inspector general's report is released, and Obama calls the findings "intolerable and inexcusable."
May 15: Obama removes Miller as acting IRS commissioner and says in televised statement: "I will not tolerate this kind of behavior in any agency but especially in the IRS, given the power that it has and the reach that it has into all of our lives." In congressional testimony, Attorney General Eric Holder says the FBI's investigation could include potential civil rights violations, false statements and potential violations of the law prohibiting federal employees from engaging in some partisan political activities.
Associated Press writer Stephen Ohlemacher contributed to this report.