When you leave employer health coverage after age 65, you have an 8-month Special Enrollment Period to sign up for Medicare Part B without late penalties. Missing this window means a 10% premium increase for every 12-month period you go without Part B—a penalty that's permanent and increases your premium for the rest of your life.
The 8-Month Part B SEP Timeline
The Special Enrollment Period starts the month after either:
- You stop working, OR
- Your employer health coverage ends, whichever comes first
Common mistake: Many people assume the 8 months start when COBRA ends. They don't. The clock starts when active employment ends or active employer coverage ends, NOT when COBRA, retiree coverage, or severance benefits end.
Form CMS-L564: Required for SEP Enrollment
To use the Part B SEP, you need to prove you had qualifying employer coverage. Social Security requires Form CMS-L564 (Request for Employment Information), which must be completed and signed by your former employer.
Steps to Complete Form CMS-L564:
- Download Form CMS-L564 from CMS.gov or get it from your local Social Security office
- Complete Section A (your personal information)
- Send the form to your former employer to complete Section B
- Submit the completed form along with Form CMS-40B (Application for Enrollment in Part B) to Social Security
- Keep copies for your records
What Coverage Triggers the SEP?
| Coverage Type | Qualifies for SEP? |
|---|---|
| Active employer group health plan (any size) | Yes |
| Spouse's active employer group health plan | Yes |
| FEHB (Federal Employees Health Benefits) | Yes |
| COBRA continuation coverage | No |
| Retiree health coverage | No |
| ACA Marketplace coverage | No |
| Medicaid | No (but you may be dual-eligible) |
| Veterans Affairs (VA) health care | No |
When Should You Actually Enroll?
Even though you have 8 months, don't wait. The longer you delay, the longer you'll go without Part B coverage. Aim to:
- Apply 1-2 months before your employer coverage ends, so Part B starts the day after employer coverage ends
- If applying after coverage ends, expect a 1-3 month wait for Part B to start
- You can request that Part B start retroactively up to 6 months (but no earlier than your 65th birthday month)
What If You Missed the SEP?
If you missed your 8-month Part B SEP, you'll have to wait for the General Enrollment Period (January 1 – March 31 each year), with Part B coverage starting July 1. You'll also owe a 10% penalty for every 12-month period you could have had Part B but didn't.
Recent change: Since 2023, Medicare allows Part B coverage to start the month after General Enrollment Period enrollment (instead of July 1), shortening the coverage gap for late enrollees.
Don't Miss Your 8-Month Window
The Part B SEP rules are detailed and unforgiving. A licensed Medicare agent can help you submit Form CMS-L564 properly and ensure your Part B starts when you need it.