After coverage based on current employment ends, an eligible person generally has up to eight months to enroll in Medicare Part B without a late-enrollment penalty. The clock starts after employment or the group health coverage ends, whichever happens first. Electing COBRA does not extend this Part B Special Enrollment Period.
An October 2026 Medicare thread proposed ending employer coverage in December but waiting until July for Part B. The dates can fit inside the eight-month period, but the narrow margin and COBRA misconception create preventable gaps.
Start here: a practical action plan
- Open the official source and confirm the rule for your coverage, tax year, filing status, and deadline.
- Collect the notices, statements, plan documents, forms, and dated confirmations that control the decision.
- Replace the hypothetical figures with your actual amounts and keep the checked calculation with your records.
- Record the next deadline and obtain written confirmation after an enrollment, correction, appeal, or payment posts.
- Treating a forum answer, portal label, or plan summary as the final authority for a coverage or tax result.
- Comparing amounts on different tax, timing, or coverage bases without converting them to the same basis first.
- Discarding dated evidence that may be needed for an enrollment, appeal, tax correction, or claim dispute.
Identify which event starts the eight-month clock
Write down the last day of current employment and the last day of group health coverage based on that employment. The Special Enrollment Period follows the earlier loss. Retiree coverage and COBRA are not current-employment coverage for this Part B rule.
Do not count eight months from the end of COBRA. Medicare says the Part B window runs whether or not COBRA is elected. A person can therefore have COBRA coverage on paper while the penalty-free Part B enrollment period is already expiring.
Collect employment evidence before the office closes the file
The Part B enrollment process can require evidence of employer group coverage. CMS-40B is the Part B application, and CMS-L564 documents employment information. Ask human resources to complete the employer section while records and contacts are easy to reach.
Keep pay stubs, coverage cards, enrollment confirmations, termination letters, and the Summary Plan Description. If the employer is acquired or closes, dated evidence becomes more important. Confirm the actual Medicare effective date rather than treating the application date as coverage.
Worked example: December coverage loss and a July start
Example: current employment and employer coverage both end December 31, 2026. The Part B Special Enrollment Period begins after that event. A requested July 1, 2027 start may fall within the eight-month window, but it leaves six months in which another plan must pay primary.
If the person uses COBRA from January through June at $950 per month, the premium bridge is $5,700. That cash cost does not change the Part B deadline. The safer timeline records application dates, requested effective dates, COBRA termination, and Medigap or Medicare Advantage decisions together.
| Milestone | Example date | Budget effect |
|---|---|---|
| Employment ends | Dec. 31, 2026 | SEP trigger |
| COBRA bridge | Jan. through Jun. 2027 | $5,700 at $950 monthly |
| Requested Part B start | July 1, 2027 | Verify approval |
| Eight-month SEP | After coverage loss | COBRA does not extend |
Coordinate Part A, HSA, drug coverage, and Medigap
Part A can be retroactive for some applicants, which matters for HSA contribution eligibility. Stop and calculate HSA months before applying. Part D has a separate creditable-drug-coverage rule, so a Part B deadline does not prove the drug deadline is safe.
If Original Medicare and Medigap are planned, the federal Medigap open-enrollment period generally begins with Part B for someone age 65 or older. If Medicare Advantage is planned, compare networks and drug coverage. Confirm every effective date before cancelling bridge coverage.
- Record employment and coverage end dates.
- Obtain CMS-L564 evidence promptly.
- Choose a Part B effective date inside the window.
- Coordinate HSA, Part D, and supplemental coverage.
Frequently asked questions
How long is the Part B Special Enrollment Period after work ends?
It generally lasts eight months after employment or employer group coverage ends, whichever occurs first.
Does COBRA extend the Part B enrollment deadline?
No. Medicare says the eight-month period runs whether or not COBRA is elected.
Which form proves employer coverage?
CMS-L564 documents employment information, and CMS-40B is used to apply for Part B in the Special Enrollment Period process.
Is retiree coverage treated as current-employment coverage?
No. Retiree coverage generally does not protect the Part B Special Enrollment Period in the same way.
Can Part A affect prior HSA contributions?
Yes. Part A can be retroactive for some delayed applicants, potentially making contributions for retroactively covered months excess.
Should I cancel COBRA when I submit the Medicare application?
Wait until Medicare and replacement coverage effective dates are confirmed in writing so a processing delay does not create a gap.
Sources and review notes
The calculations and scenarios in this guide are original BreadWinnr worked examples. We recalculated each example and checked that its parts match the stated total. Official sources support the financial concepts. Forum links document the reader problem that prompted the guide and are not treated as financial authority.
- Medicare.gov, COBRA and the Part B window
- CMS, application for Part B during a Special Enrollment Period
- Reddit: starting Medicare after employer coverage
Read our research, testing, corrections, and source policy.
This guide provides general financial education. It does not account for your complete financial, tax, legal, or contractual situation.
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