You can make a greater number of changes during AEP than OEP. You can only make a single change during the OEP.
Unlike during AEP, you can not make the following changes during OEP:
Switch from Original Medicare to a MedicareAdvantage plan.
Join a Medicare Part D (prescription drug) if you’re in Original Medicare.
Switch from one Medicare Part D (prescription drug) plan to another if you’re in Original Medicare.
OEP does not apply to Original Medicare. AEP allows people with Original Medicare to make changes to their Medicare coverage. OEP does not.