What the Part B Special Enrollment Period is
If you delayed Medicare Part B because you had creditable employer coverage from a 20+ employee company, you're entitled to a Special Enrollment Period (SEP) when that coverage ends. The SEP gives you up to 8 months to enroll in Part B without facing the 10% lifetime late-enrollment penalty.
When the 8-month clock starts
The clock starts on the date your active employee health coverage ends, or the date your employment ends — whichever happens first. It does not start when COBRA coverage ends. This is the single most expensive misunderstanding for Ohio retirees.
Concrete example: you retire June 30, 2026. Your active employee coverage ends June 30. You elect COBRA, which runs through December 31, 2027 (18 months). Your Part B SEP runs from July 1, 2026 through February 28, 2027 — the 8 months following active employee coverage ending. Not from when COBRA ends.
When your Part B coverage actually starts
If you enroll during the month active employer coverage ends, Part B coverage starts the first of the following month — but you can also request that it start retroactively up to 6 months. Otherwise, Part B starts the first of the month after you enroll.
Plan timing carefully to avoid a coverage gap: if your employer coverage ends June 30 and you want Part B effective July 1, enroll in May or June. If you enroll in August, Part B starts September 1 — a one-month gap.
The forms you'll need
- Form CMS-L564 — Request for Employment Information. Your HR department fills in dates of group health coverage. Get this from HR before they're gone.
- Form CMS-40B — Application for Enrollment in Medicare Part B. You complete this.
- Both forms together get submitted to Social Security. Online submission is available through your SSA account.
Common Ohio scenarios
Standard retirement at 65 or later
Stop work at retirement age. Employer coverage ends on your last day or end of month. You have 8 months to enroll in Part B. Most Ohioans enroll in the first month — paperwork takes time and you don't want a gap.
Layoff or reduction in hours after 65
If your hours drop below the threshold for employer coverage (typically 30 hours/week), or you're laid off, your SEP starts when active employee coverage ends. Same 8-month window.
Spouse coverage ending
If you were covered as a dependent under your spouse's employer plan and that plan ends — because your spouse retires, switches jobs, or you divorce — you get the SEP just like the employee would. The 8-month clock starts when the spousal coverage ends.
You missed the SEP
If 8 months pass without enrolling and you don't have other creditable coverage, your next opportunity is the General Enrollment Period (January 1 – March 31). Coverage starts the first of the month after enrollment. You'll face a permanent Part B late-enrollment penalty of 10% per 12-month period you went without coverage.
Special SEPs you may not know about
- Volunteers abroad: extended SEP for U.S. citizens working abroad as volunteers with a tax-exempt organization.
- Emergency or disaster SEP: CMS occasionally extends SEPs after federal disaster declarations affecting Ohio counties (tornadoes, severe storms).
- Marketplace transition SEP: limited SEP for people aging into Medicare from ACA Marketplace coverage.
What to do
- 3 months before employer coverage ends, request Form CMS-L564 from HR.
- Fill out Form CMS-40B yourself.
- Submit both to Social Security as soon as you have the L564 back from HR.
- Aim for Part B coverage to start the first of the month after your employer coverage ends.
- If anything looks complicated — early retirement, divorce, spouse death, multi-employer plans — talk to a licensed Ohio Medicare agent or OSHIIP counselor before submitting.