Internal Revenue Service officials from Washington and the Cincinnati office at the center of the controversy over IRS scrutiny of conservative groups are set to testify in Congress next week.
The House of Representatives Committee on Oversight and Government Reform said the not-yet-named officials will appear on July 18 before the panel, which is investigating the matter.
"This hearing will examine why decisions to elevate cases to more senior levels of the IRS led to unjust delays and unfair treatment of Tea Party applications," Republican Committee Chairman Darrell Issa said in a statement on Wednesday.
The controversy erupted on May 10 when an IRS official revealed the agency had subjected Tea Party and other conservative groups' applications for tax-exempt status to added review, ahead of a critical inspector general report on the issue.
Some testimony by IRS employees has already been released by Issa and his Democratic counterpart, Representative Elijah Cummings. It has highlighted mismanagement while noting that some Washington IRS officials took an active role in reviewing the cases early on.
President Barack Obama, a Democrat, said he learned of the practice when the IRS official spoke about it in May. No testimony released so far has found links to the White House.
Obama dismissed the head of the IRS days after the scandal broke. Several other officials have been put on leave.
A Treasury Inspector General for Tax Administration report in May found that "Tea Party" and other terms associated with conservative causes were put on a "be on the lookout," or BOLO list, that Cincinnati employees used to track cases.
The controversy deepened last month when the IRS released other "BOLO" lists containing key words like "Progressive." It remains unclear if liberal groups received added scrutiny comparable to that of conservative groups.