Applying for Medicare Part B when you retire is not automatic for most people, and missing the window costs you permanently. The late enrollment penalty adds 10% to your monthly premium for every 12-month period you were eligible but not enrolled, and it stays on your bill for life. This guide walks you through every step, every enrollment window, and every deadline you need to know for 2026.
What Is Medicare Part B and What Does It Cover?
Medicare Part A covers hospital stays. Medicare Part B covers outpatient care: doctor visits, preventive screenings, lab work, durable medical equipment, and most services you receive outside of a hospital.
Part B is optional in the sense that you have to actively enroll, but for most people it is essential. Without it, you have no coverage for routine doctor visits or specialist appointments.
2026 Part B costs:
| Cost | Amount |
|---|
| Standard monthly premium | $202.90 |
| Annual deductible | $283 |
| Coinsurance after deductible | 20% of Medicare-approved amount |
Higher-income enrollees pay more through IRMAA (Income-Related Monthly Adjustment Amount). If your modified adjusted gross income from two years ago exceeded $109,000 (individual) or $218,000 (married filing jointly), your premium will be higher.
The Three Enrollment Periods That Matter
Initial Enrollment Period (IEP)
This is your primary window. It opens 3 months before the month you turn 65, includes your birthday month, and closes 3 months after. Total: 7 months.
If you enroll during the 3 months before your birthday month, coverage starts on the first day of your birthday month. If you enroll during or after your birthday month, coverage is delayed by one to three months.
Most people who are not working at 65 should enroll during the IEP. If you miss it and do not qualify for a Special Enrollment Period, you will face the lifetime penalty.
Special Enrollment Period (SEP) for Retirees
This is the most important period for people who delayed Part B because they had employer health coverage through a job (their own or a spouse's).
You qualify for an SEP if:
- You were covered by a group health plan through an employer or union while you or your spouse was actively working
- The employer has 20 or more employees
The SEP lasts 8 months, starting the month after employment ends or the group health plan ends, whichever comes first. Enrolling during this window means no late penalty.
Critical warning: Retiree health coverage, COBRA, and ACA marketplace plans do not qualify as the basis for delaying Part B. Only active employer coverage from a current employer protects you from the penalty. If you retired and are on COBRA, your SEP clock is already running.
General Enrollment Period (GEP)
If you missed both the IEP and SEP, you can enroll January 1 through March 31 each year. Coverage starts July 1. You will owe the late enrollment penalty unless you qualify for an exemption.
Step-by-Step: How to Apply for Medicare Part B
Step 1: Confirm Your Situation
Before applying, determine which enrollment window applies to you:
- Turning 65 soon with no employer coverage? Use the IEP.
- Just retired or lost employer coverage? Use the 8-month SEP.
- Missed both? Use the GEP (January 1 to March 31).
Step 2: Gather Your Documents
Have these ready before you start:
- Social Security number
- Medicare card (if you already have Part A)
- Employment information from your most recent employer
- Dates of your employer health coverage
- Spouse's employment information if you delayed based on their coverage
Step 3: Complete the Required Forms
Form CMS-40B (Application for Enrollment in Medicare Part B): This is the main enrollment application.
Form CMS-L564 (Request for Employment Information): Required if you are enrolling during a Special Enrollment Period based on employer coverage. Your employer or their HR department must complete this form to verify your group health plan dates.
Download both forms at Medicare.gov or request them from your local Social Security office.
Step 4: Choose How to Submit
Online: If you already have Medicare Part A and are applying for Part B only, you can apply online through the Social Security Administration at ssa.gov/medicare/sign-up. This is the fastest method.
By phone: Call SSA at 1-800-772-1213. Representatives are available Monday through Friday, 8 a.m. to 7 p.m.
In person: Visit your local Social Security office. Find locations at ssa.gov/locator. Appointments are recommended.
By mail or fax: Download Form CMS-40B (and CMS-L564 if applicable), complete them, and mail or fax them to your local Social Security office.
Step 5: Track Your Application
SSA typically processes Part B applications within a few weeks. You will receive a notice in the mail confirming your enrollment and your coverage start date. If you applied online, you can check status by calling SSA.
Step 6: Set Up Premium Payment
Medicare Part B premiums are usually deducted automatically from Social Security retirement benefits. If you are not yet receiving Social Security, you will receive a quarterly bill and can pay by check, online through Medicare.gov, or by setting up automatic bank withdrawal.
Enrollment Scenarios and What to Do
| Your Situation | Enrollment Period | Action |
|---|
| Turning 65, no employer coverage | IEP (7 months around birthday) | Apply online or at SSA |
| Turning 65, still working with employer coverage | Delay Part B, use SEP later | Keep proof of coverage |
| Just retired, had employer coverage | SEP (8 months from job/coverage end) | File CMS-40B + CMS-L564 now |
| On COBRA after retirement | SEP window is running | Enroll during SEP, do not wait |
| On spouse's active employer plan | SEP when their employment ends | Keep proof of coverage |
| Missed IEP and SEP, no employer coverage | GEP (Jan 1 to Mar 31) | Expect late penalty |
The Late Enrollment Penalty: How Bad Is It?
The penalty is 10% of the standard Part B premium for each full 12-month period you were eligible but not enrolled. In 2026, the standard premium is $202.90.
Penalty examples:
| Years Delayed | Penalty Percentage | Added Monthly Cost | Total Monthly Premium |
|---|
| 1 year | 10% | $20.29 | $223.19 |
| 2 years | 20% | $40.58 | $243.48 |
| 3 years | 30% | $60.87 | $263.77 |
| 5 years | 50% | $101.45 | $304.35 |
The penalty recalculates each year as the base premium changes, but the percentage stays the same for life. Someone who delays 2 years and lives another 20 years could pay over $10,000 more in premiums than they would have otherwise.
When Automatic Enrollment Applies
Some people are enrolled in Medicare Part B automatically and do not need to apply:
- People who are already receiving Social Security benefits when they turn 65 are automatically enrolled in both Part A and Part B
- People under 65 who have received Social Security Disability Insurance (SSDI) for 24 months are automatically enrolled
If you are automatically enrolled and do not want Part B (for example, because you still have employer coverage), you can decline it by following the instructions in your Medicare welcome packet.
Common Mistakes to Avoid
Assuming retiree coverage protects you. Retiree health plans, COBRA, and marketplace plans are not considered qualifying employer coverage for the purpose of delaying Part B. The penalty clock starts when your or your spouse's active employment ends.
Missing the SEP window. The 8-month SEP starts the day after employment or coverage ends. It does not restart. If you miss it, you wait until the next General Enrollment Period and pay the penalty.
Delaying because you feel healthy. Part B covers preventive care, annual wellness visits, cancer screenings, and other services that catch problems early. Delaying coverage is a financial risk, not just a health one.
Not filing CMS-L564. If you are using the SEP and do not include employer verification from your HR department, SSA may reject your application or treat your enrollment as if you had no qualifying coverage.
What Comes After Part B Enrollment?
Once enrolled in original Medicare (Part A and Part B), most people add additional coverage:
- Medicare Supplement (Medigap): Covers the 20% coinsurance that Part B does not pay. Best purchased within 6 months of Part B enrollment start date, when insurers cannot deny you based on health history.
- Medicare Advantage (Part C): An alternative to original Medicare that bundles Parts A and B with other benefits through a private insurer.
- Medicare Part D: Prescription drug coverage. Has its own enrollment deadlines and late penalty.
Check your eligibility and coverage options at CoveredUSA. The screener takes about 2 minutes and helps you understand which programs you qualify for based on your age, income, and situation.
Frequently Asked Questions
When should I apply for Medicare Part B if I retire at 65?
Apply during the first 3 months of your Initial Enrollment Period (the 3 months before your 65th birthday) so coverage starts on the first day of your birthday month. If you apply during or after your birthday month, coverage is delayed by 1 to 3 months.
Can I apply for Part B without Part A?
Yes. If you do not qualify for premium-free Part A (which requires 40 quarters of Medicare-covered work), you can still enroll in Part B alone. You would pay a Part A premium as well. Most people, however, have Part A and are adding Part B.
What if I am still working at 65 and have employer health insurance?
You can delay Part B without penalty as long as your coverage is through an active employer with 20 or more employees. When you retire or that coverage ends, you have an 8-month Special Enrollment Period to sign up for Part B.
Does my spouse's employer coverage let me delay Part B?
Yes, if your spouse is actively working and you are covered under their employer's group health plan, and the employer has 20 or more employees, you can delay Part B without penalty. Your SEP begins when their employment or coverage ends.
How do I avoid the Medicare Part B late enrollment penalty?
Enroll during your Initial Enrollment Period or, if you delayed because of qualifying employer coverage, during your 8-month Special Enrollment Period. Submit Form CMS-L564 from your employer to document the coverage dates.
What is the Part B premium in 2026?
The standard Medicare Part B monthly premium in 2026 is $202.90. The annual deductible is $283. Higher-income enrollees pay more based on IRMAA brackets, which start at $109,000 in annual income for individuals.
How long does it take to process a Part B application?
Most applications are processed within a few weeks. Applications submitted by mail or fax take longer than online applications. If you are near a deadline, apply online or call SSA directly at 1-800-772-1213.
Can I get Part B if I missed my enrollment window?
If you missed both the Initial Enrollment Period and the Special Enrollment Period, you can enroll January 1 through March 31 during the General Enrollment Period. Coverage starts July 1. You will likely owe a permanent late enrollment penalty.
Understanding where you stand on Medicare Part B enrollment is one of the most financially important steps in retirement planning. Check your eligibility now at CoveredUSA. It takes 2 minutes.
Check Your Medicare Eligibility
