For Medicare beneficiaries, this is a time 3 months immediately before a person is entitled to Medicare Part A and enrolled in Part B. If he or she chooses to join a Medicare health plan during the initial coverage election period, the plan must accept him or her. The only time a plan can deny enrollment during this period is when it has reached its member limit. This limit is approved by the Centers for Medicare and Medicaid Services (CMS). The initial coverage election period is different from the initial enrollment period (IEP). See election period .