What Is the Medicare Initial Enrollment Period?

Your Medicare Initial Enrollment Period (IEP) is a 7-month window — your first and best opportunity to sign up for Medicare without Penalty. It surrounds your 65th birthday:

• 3 months before the month you turn 65
• The month you turn 65
• 3 months after the month you turn 65

Miss this window without a qualifying reason, and you may pay a late enrollment penalty on your Medicare Part B Premium for life.

Why Your Enrollment Month Inside the Window Matters

When you sign up within your IEP affects when your coverage actually starts — and the difference can be several months.

The takeaway: Sign up in the 3 months before your birthday month to get coverage starting right on time. Waiting until your birthday month or later delays your start date.

Special rule if your birthday falls on the 1st of the month: Medicare treats you as turning 65 the previous month, so your enrollment window and coverage start date shift back one month.

What Happens If You Miss Your Initial Enrollment Period?

If you miss your IEP and don’t qualify for a Special Enrollment Period, you have two options — neither is great:

General Enrollment Period (GEP): January 1 – March 31 each year. You can sign up during this window, but you’ll likely pay a permanent Part B late enrollment penalty — 10% added to your premium for every 12-month period you were eligible but didn’t enroll. That penalty stays with you for as long as you have Part B.

Special Enrollment Period (SEP): If you delayed Medicare because you had active employer group coverage (through your own job or a spouse’s), you may qualify for a Special Enrollment Period. This lets you sign up without penalty. See how this works →

Should You Enroll in Medicare at 65 Even If You’re Still Working?

It depends on your employer’s size and your coverage situation.

If your employer has 20 or more employees: Your Group health plan is primary. You can generally delay Medicare Part B without penalty as long as you maintain that coverage through active employment. You’ll have an 8-month Special Enrollment Period once your coverage ends or employment ends, whichever comes first.

If your employer has fewer than 20 employees: Medicare becomes your primary payer at 65. In most cases, you should enroll in both Part A and Part B on time to avoid gaps or penalties.

COBRA and retiree coverage do not count as active employer coverage for Medicare SEP purposes. If you leave your job and go on COBRA, your clock is running on the Part B penalty.

Part A vs. Part B: Do You Need Both?

Medicare Part A (hospital insurance) is premium-free for most people and can generally be enrolled in any time after your IEP starts without penalty. Most people enroll in Part A at 65 even if they delay Part B.

Medicare Part B (medical insurance) requires a monthly premium ($202.90 in 2026) and carries a late enrollment penalty if you miss your window without a qualifying excuse. This is the enrollment decision that most people need to think through carefully.

Frequently Asked Questions

Can I enroll in Medicare before I turn 65?
Yes — your Initial Enrollment Period starts 3 months before your 65th birthday month. Enrolling early in that window gets you the earliest possible coverage start date.

What if my birthday is on the 1st of the month?
Medicare considers you to have turned 65 the month before your actual birthday. So if you turn 65 on July 1, Medicare treats you as turning 65 in June, shifting your entire enrollment window one month earlier.

Does the Initial Enrollment Period apply to Medicare Supplement (Medigap) plans too?
Not exactly. Your Medigap Open Enrollment Period — the 6-month window when insurers cannot deny you coverage or charge more due to health conditions — begins when you have both Medicare Part B and are age 65 or older. It often overlaps with but is separate from your IEP. Use our Medigap Open Enrollment Calculator to find your Medigap window.

What if I’m under 65 and getting Medicare due to disability?
Your enrollment rules are different. You’ll receive Medicare automatically after 24 months of Social Security disability benefits (immediately if you have ALS). Your Medigap open enrollment rights may also differ by state. Contact us and we can walk you through your specific situation.

I missed my window. What do I do now?
Talk to a REMEDIGAP advisor — we can help you understand whether you qualify for a Special Enrollment Period, what the General Enrollment Period means for you, and how to minimize any penalty if one applies.

Ready to Take the Next Step?

Once you know your enrollment window, the next decision is which Medicare coverage to choose. Most people turning 65 choose between a Medicare Supplement (Medigap) plan and Medicare Advantage.

Download our free Medicare Checklist to see everything you need to decide — and in what order — before your coverage starts.