If you kept working past 65 and stayed on a health plan from your job (or your spouse's job), you probably put off Part B. That's allowed. When the job or the coverage ends, Medicare gives you a limited time to sign up for Part B without a late penalty. This is the Part B Special Enrollment Period, often called the SEP.
This page covers who qualifies, how to count your 8 months, and what happens if you miss them.
The rule in one sentence
You can sign up for Part B in any month you're covered by a group health plan based on your or your spouse's current job, or in the 8 months that start the month after the job or the coverage ends, whichever happens first (POMS HI 00805.275).
The window closes on the last day of the eighth month (42 CFR 406.24).
Who qualifies
For people 65 and older, it comes down to three questions.
1. Is the coverage from current work?
The plan has to be based on the current employment of you or your spouse (42 CFR 407.20). That means you're actively working as an employee, you're the employer or self-employed, or you have a business relationship with the employer. Some people who aren't working right now can still count, such as people on sick leave, furlough or a temporary layoff whose employer hasn't ended their job, if certain other conditions are met (POMS HI 00805.266). COBRA never counts.
A divorced spouse covered by a former spouse's job-based plan counts as a spouse for this rule.
2. Does the size of the employer matter?
No. If you have Medicare because of your age, the plan can come from an employer of any size (POMS HI 00805.266). Small employers do follow a different rule about who pays first. See working past 65 at a small employer.
3. Have you been covered since you first became eligible?
You must have had job-based coverage from current work, or Part B, in your first month of Part B eligibility and in every month since (42 CFR 407.20; POMS HI 00805.270). The CMS-L564 form says the same thing at the top.
One kind of break is forgiven. If your job or coverage ends and you get current-employment coverage again before the 8 months run out, the earlier window is treated as if it never happened (POMS HI 00805.275).
Coverage that does not count
- COBRA. It is never coverage from current work. See COBRA and Part B.
- Retiree coverage from a former employer. See retiree coverage and Part B.
- Marketplace (Healthcare.gov) or other individual plans.
- An Individual Coverage HRA (ICHRA).
- TRICARE based on past military service. Only TRICARE based on active duty counts.
- VA coverage. Social Security warns that if you skip Part B when first eligible, you may owe a penalty and have to wait to enroll.
People whose Medicare is based on end-stage renal disease (ESRD) also can't use this SEP.
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How to count your 8 months
- Write down the last month you (or your spouse) worked.
- Write down the last month you had the job-based coverage.
- Take whichever month is earlier. Your 8 months start the month after it.
A partial month counts as a full month (POMS HI 00805.275). If your coverage ends on the 10th, that whole month counts as a covered month.
| Your situation | Month that starts the clock | Your 8 months | Last day |
|---|---|---|---|
| Job and coverage both end in December 2026 | December 2026 | January to August 2027 | August 31, 2027 |
| You stop working in March 2027, but the plan covers you through April 2027 | March 2027 (work ended first) | April to November 2027 | November 30, 2027 |
| Your last day of work and coverage is October 10, 2026 | October 2026 (partial month counts) | November 2026 to June 2027 | June 30, 2027 |
| You're still working and covered | Not started yet | Any month while covered | None yet |
The second row surprises people. Social Security puts it this way: you have 8 months from when you or your spouse stop working, "even if your group health plan continues for a time."
Special cases
- Two job-based plans. The clock starts after the last month you had coverage under any of them.
- Coverage ended after the fact. If you're told your coverage ended retroactively, your 8 months start the month after you're notified.
- The worker died. A surviving spouse who was on the worker's plan gets 8 months starting the month after the death.
You don't have to wait for the job to end
You can sign up any month while you're still covered. Signing up early gives you the most control over your start date. If you sign up while covered, or in the first full month after coverage ends, Part B can start in the month you sign up or any of the next 3 months (POMS HI 00805.276). Medicare.gov suggests signing up about a month before your coverage ends. Details are in when does Part B start.
Not during your Initial Enrollment Period
Your Initial Enrollment Period is the 7 months around your 65th birthday: the 3 months before the month you turn 65, that month, and the 3 months after. Social Security says: "You can't enroll using an SEP until your IEP is over." If you sign up during those 7 months, it's handled as an Initial Enrollment Period sign-up, with its own start-date rules (POMS HI 00805.275).
If you miss the window
Missing the 8 months has real costs
You'll have to wait for the General Enrollment Period (January 1 to March 31), and Part B starts the month after you sign up. You may also owe a late penalty for as long as you have Part B (SSA Publication 05-10043).
- The penalty is 10% for each full 12 months you could have had Part B but didn't. Months you had job-based coverage from current work don't count. See how the penalty is counted.
- If you let an available SEP pass, you generally don't get another one, unless current-employment coverage came back before that window ended (42 CFR 407.20).
- If an employer, health plan, agent or broker gave you wrong information on or after January 1, 2023, and that's why you missed it, you may qualify for an "exceptional conditions" SEP using form CMS-10797.
What you'll send
- CMS-40B, if you already have Part A. It's the request to enroll in Part B.
- CMS-L564, filled in by you and your employer. It's your proof of job-based coverage.
You can send them online, by fax, by mail or in person. See how to submit the forms.