Initial Enrollment Period (IEP)
Your IEP is a seven-month window built around your 65th birthday: the three months before your birthday month, your birthday month, & the three months after. Enrolling in the first three months usually means coverage starts the first day of your birthday month. Waiting until your birthday month or later pushes your start date back.
Annual Enrollment Period (AEP): October 15 – December 7
This is the window most people use. During AEP you can switch between Original Medicare & Medicare Advantage, change Advantage plans, join or drop a Part D plan, or switch drug plans. Changes take effect January 1.
- Review your Annual Notice of Change letter each September — plans change formularies, networks & copays every year.
- Re-check your drug list annually even if you are happy with your plan.
- Confirm your doctors are still in network for the coming year.
Medicare Advantage Open Enrollment: January 1 – March 31
If you are already in a Medicare Advantage plan on January 1, you get one change: switch to a different Advantage plan, or drop back to Original Medicare & add a standalone Part D plan. You cannot use this window to join an Advantage plan from Original Medicare.
General Enrollment Period: January 1 – March 31
For people who missed their IEP & have no Special Enrollment Period. Coverage begins the first of the month after you sign up, & late-enrollment penalties usually apply.
Special Enrollment Periods (SEPs)
- Losing employer or union coverage.
- Moving out of your plan's service area.
- Qualifying for Medicaid or Extra Help.
- Your plan leaving the market or losing its Medicare contract.
- Living in an area affected by a FEMA-declared emergency.
What late enrollment actually costs
- Part B: roughly 10% added to your premium for each full 12-month period you could have had Part B but didn't — for as long as you have Part B.
- Part D: about 1% of the national base beneficiary premium for each month you went without creditable drug coverage, added permanently.
- Part A (if you have to buy it): a limited-term premium increase.
Frequently asked questions
I'm turning 65 but still working. When should I enroll?+
Talk to your employer's benefits administrator first. Employer plans at companies with 20+ employees are usually primary, which can let you delay Part B penalty-free. Small-employer plans often are not, & delaying could leave you with gaps plus a penalty.
Can I change Medicare Supplement plans any time?+
You can apply any time, but outside your six-month Medigap Open Enrollment window insurers in most states may use medical underwriting & decline you or charge more.
For educational purposes only. Alliance Global Insurance Group is not affiliated with or endorsed by Medicare.gov or the U.S. government. Plan availability, costs & rules vary by county & change annually — confirm details with a licensed advisor or at Medicare.gov.