The continued success of the Combined Federal Campaign (CFC), which is administered by the Office of Personnel Management (OPM), is predicated on donor confidence that each donation reaches a legitimate charitable organization. The Ways and Means Committee's review of tax-exempt entities has led to concerns that charities listed in CFC are failing to remit payroll and other taxes to IRS as required by law. Specifically, GAO was asked to determine whether and to what extent (1) charities listed in the 2005 CFC have unpaid payroll and other taxes; (2) selected charities, their directors, or senior officers are abusing the federal tax system; and (3) OPM screens charities for federal tax problems before allowing them to be listed with CFC.