How long is the Medicare Initial Enrollment Period?

The Medicare Initial Enrollment Period (IEP) is 7 months long. It starts 3 months before the month you turn 65, includes your birthday month, and ends 3 months after your birthday month. For example, if you turn 65 in June 2026, your IEP runs from March 1 through September 30, 2026.

What happens if I miss my Medicare Initial Enrollment Period?

If you miss your IEP without a qualifying Special Enrollment Period, you must wait for the General Enrollment Period, which runs January 1 through March 31 each year. Coverage then starts July 1 of that year. You may also owe a permanent Part B late enrollment penalty of 10% for each full 12-month period you were without Part B coverage. In 2026, the base Part B premium is $202.90/month, so a two-year delay adds $40.58/month permanently.

When should I sign up for Medicare to have coverage on my 65th birthday?

To have Medicare coverage starting on the first day of your birthday month, you need to enroll during the 3-month period before your birthday month. If you enroll during or after your birthday month, your coverage start date is delayed by 1 to 3 months depending on when you sign up.

Initial Enrollment Period Assessment Tool

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Key takeaway: Your Initial Enrollment Period is a fixed 7-month window tied to your 65th birthday — miss it and you could wait over a year for coverage to start while paying penalties for the rest of your life.

What this helps you decide

Exactly when your 7-month enrollment window opens and closes based on your birthday
Which month to enroll in for your coverage to start on Day 1 of Medicare eligibility
What happens if your birthday falls in January (your window starts the prior October)
What you're risking — in dollars and months of lost coverage — if you miss the window entirely

Who this is for

Someone approaching 65 who hasn't signed up for Medicare yet and wants to know their exact deadline
A person turning 65 in early or late in the year who wonders whether the prior-year rule applies to them
Anyone who missed their IEP and wants to understand the General Enrollment Period as a fallback — and what that delay actually costs
A family member helping an aging parent figure out their Medicare start date before they retire

Example results

Example 1 — Turning 65 in June 2026. Your IEP opens on March 1, 2026 (three months before your birthday month) and closes on September 30, 2026 (three months after). That gives you a full seven months to enroll. If you sign up in March, April, or May — before your birthday month — your Part B coverage starts June 1, 2026, the first day of your birthday month. If you wait until June, July, August, or September, coverage starts one to three months after you sign up. Signing up as early as possible in your IEP is the easiest way to make sure there's no gap.

Example 2 — Turning 65 in January 2026. Medicare applies a special rule: if your birthday falls in January, your IEP starts three months earlier, which lands in October of the prior year. So your window runs October 1, 2025 through April 30, 2026. This catches people off guard because their window is already open before the calendar year even begins. If you turned 65 in January 2026 and didn't know to look in late 2025, your window is still open through April 2026 — but don't wait. The "three months before" rule is calculated from your birthday month, not the calendar year.

Example 3 — Missed the IEP entirely. Say you turned 65 in March 2025 and your IEP closed June 30, 2025. You didn't sign up, and now it's late 2025. Your next chance is the General Enrollment Period, which runs January 1 through March 31, 2027. Coverage won't start until July 1, 2027 — over two years after you first became eligible. On top of the wait, you'll owe a permanent Part B late penalty of 10% per full 12-month period you were without coverage. At $202.90/mo, a two-year delay adds $40.58 to your monthly premium every single month for life. That's $486.96 in extra premiums every year, permanently.

Sample scenarios

Scenario	Input	Result
Birthday in June 2026	Enrolls in April (month before birthday month)	IEP: Mar 1 – Sep 30, 2026. Coverage starts June 1, 2026.
Birthday in January 2026	Enrolls in November 2025	IEP: Oct 1, 2025 – Apr 30, 2026. Coverage starts January 1, 2026.
Missed IEP (turned 65 in March 2025)	Didn't enroll during IEP	Next window: Jan–Mar 2027. Coverage July 2027. Penalty: +$40.58/mo permanently.
Birthday in October 2026	Enrolls in July 2026	IEP: Jul 1 – Jan 31, 2027. Coverage starts October 1, 2026.

What to do next

Find your birthday month and count back three months — that's the first day of your IEP. Mark it on your calendar right now.
To get coverage starting on your 65th birthday, aim to enroll during those three months before your birthday month, not after.
If you have employer coverage through a job or a spouse's job, check whether you qualify for a Special Enrollment Period — you may be able to delay without penalty.
If you've already missed your IEP, use the late enrollment penalty calculator to see exactly what you'll owe, then plan to enroll during the next General Enrollment Period (January–March each year).

Key facts

The Initial Enrollment Period (IEP) is a 7-month window: the 3 months before, the month of, and the 3 months after your 65th birthday month. It applies to both Medicare Part A and Part B.
Missing the IEP means waiting for the General Enrollment Period (January 1–March 31 each year), with coverage starting July 1 — a gap that can exceed 12 months from your original eligibility date.
Enrolling after your birthday month during the IEP (months 5, 6, or 7) delays your coverage start by 1–3 months beyond your enrollment date, so earlier is better.

Related decisions

Decision area	Tool	What it answers
Enrollment	Initial Enrollment Period Calculator	When your 7-month Medicare eligibility window begins and ends based on your 65th birthday
Enrollment	When Should I Sign Up for Medicare?	The best time to enroll based on your work status, other coverage, and age
Enrollment	Special Enrollment Period Checker	Whether a life event qualifies you for enrollment outside the standard windows
Enrollment	Late Enrollment Penalty Checker	How much extra you'll pay monthly if you missed your enrollment window
Enrollment	Part B Penalty Calculator	The exact 10%-per-year premium increase for delayed Part B enrollment
Enrollment	Part D Penalty Calculator	The 1%-per-month premium increase for gaps in creditable drug coverage
Costs	Cost Scenario Planner	Estimated annual spending across plan types at different health utilization levels
Costs	Advantage vs. Medigap Cost Comparison	True cost difference between Medicare Advantage and Original Medicare with Medigap
Costs	IRMAA Calculator	Whether your income triggers higher Part B and Part D premiums
Costs	Part A Premium Estimator	Your monthly Part A premium based on work history and quarters of coverage
Costs	M3P Calculator	How the Medicare Prescription Payment Plan smooths your drug costs into monthly payments
Coverage	Doctor & Drug Assessment	Whether your providers and prescriptions are covered by a specific plan
Coverage	Part D Shopping Tool	Which Part D plan has the lowest total annual cost for your specific medications
Coverage	Travel & Network Risk Assessment	How your coverage works outside your home area and which plan types travel best
Employer/COBRA	COBRA vs. Medicare	Why COBRA can trigger permanent Medicare penalties and how costs compare
Employer/COBRA	Employer Coverage vs. Medicare	Whether your employer plan or Medicare is primary and when to transition
Employer/COBRA	HSA & Medicare Compatibility	How Medicare enrollment affects HSA eligibility and what to do before enrolling
Planning	Caregiver Readiness Checklist	Whether you have everything in place to help a loved one with Medicare decisions
Planning	Document Gatherer	Which documents you need to have ready before enrolling or changing plans
Planning	Medigap Fit Assessment	Whether Medigap or Medicare Advantage is the better fit for how you use healthcare
Planning	Medigap Open Enrollment Window	Whether you're inside your one-time guaranteed issue window for Medigap
Planning	Medicare Savings Program Eligibility	Whether your income qualifies you for help paying Medicare premiums and cost-sharing