Article Excerpt: "...If you retire voluntarily on an immediate annuity which is not reduced for age, you may be eligible for the annuity supplement, in addition to your regular monthly FERS benefit. You may also receive the supplement if you retired involuntarily before attaining your Minimum Retirement Age (MRA) or voluntarily because of a major reorganization, reduction in force, or an early retirement for Members of Congress. However, in these three instances, you will not be eligible for the annuity supplement until you reach your Minimum Retirement Age (MRA). If you receive a deferred benefit, a disability benefit or an immediate MRA+10 benefit, you will not be eligible for the annuity supplement...."
Resource: www.opm.gov
FERS Annuity Supplement