Missing a Medicare enrollment window is not a one-time inconvenience. For most people, a late Part B enrollment triggers a permanent monthly surcharge that lasts for the rest of their lives. As of 2026, the standard Part B premium is $202.90 per month. Miss two full years of enrollment and that number goes up 20% forever. Understanding each enrollment window and its deadlines is one of the most financially consequential things a Medicare-eligible person can do.
Quick Answer: Medicare has five main enrollment windows in 2026: the Initial Enrollment Period (IEP), Annual Enrollment Period (AEP, Oct 15 to Dec 7), General Enrollment Period (GEP, Jan 1 to Mar 31), Medicare Advantage Open Enrollment Period (MA OEP, Jan 1 to Mar 31), and Special Enrollment Periods (SEPs) triggered by qualifying life events. Missing your IEP without a valid SEP reason leads to permanent premium penalties on Parts B and D.
The Five Medicare Enrollment Windows for 2026
Medicare does not work like most insurance. You cannot simply sign up at any time. CMS (the Centers for Medicare and Medicaid Services) defines specific windows when enrollment is allowed. Each window has different eligibility rules, deadlines, and coverage start dates.
1. Initial Enrollment Period (IEP)
The IEP is your first and most important opportunity to enroll in Medicare. It is a 7-month window centered on your 65th birthday:
- Months 1-3: The three months before your birthday month
- Month 4: Your birthday month
- Months 5-7: The three months after your birthday month
Example: If you turn 65 in September 2026, your IEP runs from June 1 through December 31, 2026.
When you enroll matters for your coverage start date:
| When You Enroll During IEP | Coverage Starts |
|---|
| Months 1, 2, or 3 (before birthday month) | The month you turn 65 |
| Month 4 (birthday month) | The following month |
| Month 5 | Two months after birthday month |
| Month 6 or 7 (after birthday month) | Three months after birthday month |
IEP for disability: People under 65 who qualify for Medicare due to disability have their IEP begin 3 months before the 25th month of receiving Social Security Disability Insurance (SSDI) benefits.
2. Annual Enrollment Period (AEP)
The 2026 AEP runs October 15 through December 7, 2026. Changes made during this window take effect January 1, 2027.
During AEP, you can:
- Switch from Original Medicare (Parts A and B) to a Medicare Advantage plan
- Switch from Medicare Advantage back to Original Medicare
- Switch from one Medicare Advantage plan to another
- Enroll in, drop, or switch a Part D prescription drug plan
The AEP is sometimes called "Open Enrollment" but it is not a first-enrollment opportunity for those who missed their IEP. That is what the GEP is for.
3. General Enrollment Period (GEP)
The GEP runs January 1 through March 31 each year. In 2026, coverage for GEP enrollees starts July 1, 2026.
The GEP is a safety net for people who missed their IEP and do not qualify for a SEP. There are two significant downsides to using the GEP instead of enrolling during the IEP:
- Late enrollment penalties apply (see the penalty section below)
- A coverage gap: you enroll in early 2026 but coverage does not start until July 1
The GEP was updated in 2023. If you enroll in Part B during the GEP, your Part A and Part B coverage now starts the first day of the month after you enroll, not July 1 as it previously did. However, late enrollment penalties still apply.
4. Medicare Advantage Open Enrollment Period (MA OEP)
The MA OEP runs January 1 through March 31, 2026. It is exclusively for people who are already enrolled in a Medicare Advantage plan.
During the MA OEP, you can:
- Switch to a different Medicare Advantage plan
- Drop your Medicare Advantage plan and return to Original Medicare (and add a Part D plan)
You cannot use the MA OEP to enroll in Medicare for the first time, and you cannot switch from Original Medicare to Medicare Advantage during this window.
5. Special Enrollment Periods (SEPs)
SEPs allow you to enroll outside the standard windows when a qualifying life event occurs. Unlike the AEP or GEP, SEPs are triggered by specific circumstances.
Common qualifying events for a SEP:
| Qualifying Event | SEP Duration |
|---|
| Losing employer or union coverage | 8 months from the date coverage ends |
| Moving out of your plan's service area | Generally 2 months from the move |
| Qualifying for Medicaid or Extra Help (LIS) | Year-round enrollment in most cases |
| Moving into or out of a nursing home | Generally 2 months |
| Your plan leaves Medicare or loses its contract | Varies by circumstance |
The employer coverage SEP is the most commonly used. If you are still working at 65 and covered by employer group health insurance, you can delay Part B without penalty. Your 8-month SEP begins when that employer coverage ends or the employment ends, whichever comes first. Note: COBRA or retiree insurance does not count as employer coverage for SEP purposes.
Medicare Late Enrollment Penalties in 2026
Late enrollment penalties are calculated differently for each part of Medicare. All figures below reflect 2026 rates as published by CMS.
Part B Late Enrollment Penalty
The Part B penalty is 10% of the standard monthly premium for each full 12-month period you were eligible but did not enroll. In 2026, the standard Part B premium is $202.90 per month.
| Years Late | Penalty Percentage | Monthly Penalty Added | Total Monthly Premium |
|---|
| 1 year | 10% | $20.29 | $223.19 |
| 2 years | 20% | $40.58 | $243.48 |
| 3 years | 30% | $60.87 | $263.77 |
| 4 years | 40% | $81.16 | $284.06 |
| 5 years | 50% | $101.45 | $304.35 |
The Part B penalty is permanent. It lasts for as long as you have Part B coverage. If you are late by two years and pay the $40.58 monthly penalty, you will pay that surcharge every month for the rest of your life.
Part D Late Enrollment Penalty
The Part D penalty is 1% of the national base beneficiary premium for each month you went without creditable drug coverage. In 2026, the national base beneficiary premium is $38.99 per month (per CMS).
Example: If you went 24 months without Part D coverage, your penalty is 24 x 1% x $38.99 = $9.36 per month added to your Part D premium. Like Part B, this penalty is permanent.
The penalty does not apply if you had creditable prescription drug coverage (typically from an employer plan) during the gap period. "Creditable" means the coverage is at least as good as standard Medicare Part D.
Part A Late Enrollment Penalty
Most people (those with at least 40 quarters of Medicare taxes paid) qualify for premium-free Part A and face no penalty. If you must pay for Part A and enroll late, your monthly premium increases by 10%, and you pay that penalty for twice the number of years you delayed enrollment.
In 2026, premium Part A costs between $311 and $565 per month depending on your work history.
How to Apply: Step-by-Step Enrollment for 2026
Whether you are enrolling for the first time during your IEP or during a SEP, the process is the same.
Enrollment window: If you are turning 65 in 2026, your IEP window and specific dates depend on your birthday month. Find your 7-month window using the IEP chart above.
Step 1: Gather your documents. You will need:
- Proof of identity (driver's license or passport)
- Social Security number
- Medicare card (if you already have Part A)
- Proof of creditable employer coverage (Form CMS-L564 from your employer, if using a SEP)
- Date employer coverage will end (for SEP enrollees)
- Immigration documents if you are not a U.S. citizen
Step 2: Choose your Medicare path. Decide between:
- Original Medicare (Parts A and B) with an optional Part D drug plan and Medigap supplement
- Medicare Advantage (Part C), which combines Parts A, B, and usually D
Step 3: Apply online, by phone, or in person.
- Online: SSA.gov/benefits/medicare
- Phone: 1-800-772-1213 (TTY: 1-800-325-0778)
- In person: At your local Social Security office
If you are already receiving Social Security retirement benefits when you turn 65, you are automatically enrolled in Parts A and B and will receive your Medicare card in the mail. You can decline Part B if you have qualifying employer coverage.
Step 4: Add Part D or a Medicare Advantage plan. Visit Medicare.gov/plan-compare to compare drug plans and Medicare Advantage options in your area.
Step 5: Review your Summary of Benefits. Once enrolled, confirm your coverage start date and premium amounts. Keep your plan confirmation documents.
Common reasons enrollments are delayed or denied:
- Proof of creditable employer coverage not submitted on time (Form CMS-L564)
- Enrolling after the SEP window has closed (more than 8 months after employer coverage ends)
- Applying during the wrong enrollment period for the plan type
- Incomplete documentation for non-citizen enrollees
Who Qualifies for Medicare in 2026
Medicare eligibility does not depend on income. The main pathways as of 2026:
Age pathway: U.S. citizens and permanent residents who are 65 or older and have at least 40 quarters (10 years) of Medicare-covered employment, or are married to someone who does.
Disability pathway: People under 65 who have received SSDI benefits for 24 consecutive months automatically qualify for Medicare.
ESRD pathway: People of any age with End-Stage Renal Disease (permanent kidney failure requiring dialysis or a transplant) qualify immediately.
ALS pathway: People diagnosed with ALS (Lou Gehrig's disease) qualify for Medicare the same month they begin receiving SSDI, with no 24-month wait.
Check your eligibility in 2 minutes at CoveredUSA.
Medicare vs. Medicaid: Enrollment Period Differences
A common source of confusion: Medicaid has no enrollment periods. You can apply for Medicaid at any time throughout the year if your income qualifies. Medicare, by contrast, has specific windows as described above.
Many people qualify for both. These individuals are called "dual eligibles." Being enrolled in Medicaid can trigger a Special Enrollment Period for Medicare Part D and may qualify you for the Low Income Subsidy (Extra Help), which reduces Part D costs significantly.
Learn more about Medicare eligibility requirements at /medicare-eligibility.
2026 Medicare Enrollment Period Calendar
| Enrollment Period | 2026 Dates | Who It Is For |
|---|
| Initial Enrollment Period (IEP) | 7-month window around your 65th birthday | People turning 65 for the first time |
| Annual Enrollment Period (AEP) | Oct 15 to Dec 7, 2026 | All Medicare enrollees, plan changes |
| General Enrollment Period (GEP) | Jan 1 to Mar 31, 2026 | People who missed their IEP |
| MA Open Enrollment Period (MA OEP) | Jan 1 to Mar 31, 2026 | Current Medicare Advantage enrollees only |
| Special Enrollment Period (SEP) | Triggered by qualifying events | People with life events (job loss, move, etc.) |
Frequently Asked Questions
When does my Medicare Initial Enrollment Period start?
Your IEP starts 3 months before the month you turn 65. If you turn 65 on any day in October 2026, your IEP begins July 1, 2026 and ends January 31, 2027. The 7-month window gives you flexibility, but enrolling in the first 3 months (before your birthday month) means coverage starts on your birthday month without a delay.
What happens if I miss my Medicare Initial Enrollment Period?
If you miss your IEP and do not have a qualifying event for a SEP, you must wait until the General Enrollment Period (January 1 to March 31). Coverage will start the first day of the month after you enroll. You will also owe a permanent Part B late enrollment penalty of 10% per year missed, plus a potential Part D penalty.
Can I delay Medicare if I still have employer insurance?
Yes. If you are actively working and covered by your employer's group health plan (or your spouse's employer plan), you can delay both Part B and Part D without penalty. Your SEP begins when that coverage ends, and you have 8 months to enroll in Part B without penalty. File Form CMS-L564 with your employer to document your creditable coverage status.
Does COBRA coverage let me delay Medicare enrollment?
No. COBRA is not considered employer group health coverage for Medicare SEP purposes. If your employer coverage ends and you elect COBRA, your 8-month SEP begins on the date your employer coverage ended, not when COBRA ends. Waiting until COBRA expires to enroll in Medicare will result in a coverage gap and potential late enrollment penalties.
What is the 2026 Medicare Part B premium?
The standard 2026 Medicare Part B premium is $202.90 per month, up from $185.00 in 2025. Higher-income enrollees pay Income-Related Monthly Adjustment Amounts (IRMAA) on top of this base premium. IRMAA applies if your modified adjusted gross income from two years prior (2024) exceeded $109,000 for individuals or $218,000 for joint filers.
How is the Part D late enrollment penalty calculated in 2026?
The penalty is 1% of the 2026 national base beneficiary premium ($38.99) multiplied by the number of full months you went without creditable drug coverage. For example, 18 uncovered months equals 18 x 1% x $38.99 = $7.02 added to your monthly Part D premium, permanently.
What counts as creditable drug coverage?
Coverage is "creditable" if it is at least as good as standard Medicare Part D. Most employer and union drug plans qualify. Your plan administrator is required to send you a notice each year confirming whether your coverage is creditable. Keep these notices. You may need to show proof of creditable coverage to avoid the Part D penalty when you eventually enroll.
Can I switch Medicare plans during the General Enrollment Period?
No. The GEP is only for people enrolling in Part A and/or Part B for the first time (those who missed their IEP). If you are already enrolled in Medicare and want to change your Medicare Advantage or Part D plan, you must wait for the Annual Enrollment Period (October 15 to December 7) or qualify for a SEP.
Sources: Medicare.gov, Avoid Late Enrollment Penalties | CMS 2026 Medicare Parts A and B Premiums and Deductibles | Medicare.gov Plan Compare | SSA.gov Medicare Enrollment
