Medicare Enrollment Period Comparison Calculator
Compare enrollment periods and determine your best option.
Selected Period: IEP
Period:October - April (around age 65)
Duration:7 months
Penalty Risk:None
Coverage Starts:Birthday month or following
Best For:Most people without employer coverage
Initial Enrollment Period (IEP)
Window:October - April
Duration:7 months
Penalty:None
7-month window around 65th birthday: 3 months before + birthday month + 3 months after.
Special Enrollment Period (SEP)
Trigger:Losing employer coverage or stopping work
Duration:8 months
Available:Yes
SEP available for large employer (20+) coverage. 8 months after employment or coverage ends.
General Enrollment Period (GEP)
Period:January 1 - March 31 each year
Coverage:July 1 of that year
Penalty:May apply
Only use if missed IEP/SEP. Late enrollment penalty applies. Coverage delayed to July 1.
Annual Enrollment Period (AEP)
Period:October 15 - December 7
Purpose:Change Medicare Advantage or Part D plans
Coverage:January 1 of following year
For changing plans, not initial enrollment. Switch Medicare Advantage or Part D plans.
Recommended Enrollment Strategy
SEP (if delaying due to employer coverage)
Based on your employer coverage status and size. Enroll early to avoid penalties.
Enrollment Period Key Points
- IEP: 7-month window at age 65 (best for most)
- SEP: 8 months after large employer coverage ends
- GEP: Jan-Mar annually, but penalty may apply
- AEP: Oct-Dec for plan changes, not enrollment
- MA OEP: Jan-Mar for Medicare Advantage changes
- Large employer (20+): SEP available
- Small employer: No SEP, enroll in IEP
- Enroll early in IEP for earlier coverage start
- Missing IEP/SEP leads to GEP with penalty
- Plan enrollment periods carefully