If you're retiring after age 65 and have delayed Medicare Part B because you had active employer health coverage, your retirement creates an important Medicare transition. You'll generally need to coordinate the end of your employer coverage with Medicare Part B, decide whether you want Original Medicare with a Medicare Supplement and Part D or Medicare Advantage, and make sure your new coverage begins without a gap.
For someone age 65 or older who delayed Part B while working, the start of Part B can also start a six-month Medigap Open Enrollment Period — an important opportunity to buy Medicare Supplement coverage without medical underwriting.
No obligation. One-on-one help with a licensed Medicare advisor — not a call center.
In This Guide
At a Glance
Get both dates in writing. Your Part B SEP generally begins when employment ends or job-based coverage ends, whichever happens first.
File Form CMS-40B (and CMS-L564, if applicable) with Social Security during your Special Enrollment Period.
Decide how you want to receive your Medicare benefits going forward.
In most states, benefits are standardized by plan letter — the company and premium are what differ.
Medigap doesn't include drug coverage, so pair it with a standalone Part D plan.
Line up employer coverage ending with Part B, Medigap, and Part D starting to avoid a coverage gap and understand any period of overlap.
Timing
If your employer health coverage was based on your (or your spouse's) active employment, you generally get an 8-month Part B Special Enrollment Period that starts the earlier of: the month your employment ends, or the month your employer coverage ends — whichever comes first. Signing up during that window avoids the Part B late-enrollment penalty.
As of 2023, coverage timing also got simpler: when you enroll during your Special Enrollment Period, Part B generally starts the first day of the month after you sign up — not the multi-month delay that used to apply. That makes it realistic to time your Part B start date to line up closely with your retirement date.
Easy to Miss
If you've delayed Medicare while contributing to a Health Savings Account, this needs extra planning.
Premium-free Part A can be retroactive for up to six months when you enroll after 65 — and once Part A coverage begins, you're no longer eligible to contribute to an HSA. Because of that retroactive start date, Medicare advises stopping HSA contributions six months before you retire or apply for Social Security benefits, whichever comes first, to avoid an excess-contribution tax penalty.
This timing is easy to miss because it depends on when Part A coverage ends up starting retroactively, not just your Medicare enrollment date. Check the timing with your benefits team or a tax professional before contributing during that six-month window.
Two Different Clocks
This is one of the most common points of confusion for people retiring after 65: the Part B Special Enrollment Period and the Medigap Open Enrollment Period are not the same window, and they don't last the same length of time.
| Enrollment window | What it applies to | Length |
|---|---|---|
| Part B Special Enrollment Period | Signing up for Medicare Part B after employer coverage based on active employment ends | Up to 8 months |
| Medigap Open Enrollment Period | Buying a Medicare Supplement policy without medical underwriting | 6 months, beginning when you're 65+ and enrolled in Part B |
Both windows can be running at overlapping times, but they're triggered differently and end at different points — missing one doesn't necessarily mean you've missed the other, and vice versa.
The Money Question
Your Medigap Open Enrollment Period isn't tied to your birthday — it's tied to when you're first enrolled in Part B. It starts the first day of the month you're both age 65 or older and enrolled in Part B, and it lasts six months.
If you delayed Part B because you had employer coverage, your six-month window doesn't start until Part B actually starts — even if that's well after your 65th birthday. During this window, insurers generally cannot deny you or charge you more because of your health. A limited waiting period can still apply to coverage of a pre-existing condition in some circumstances.
A Common Worry
If this is your first time enrolling in Part B — because you delayed it while covered by an employer plan — your Medigap Open Enrollment Period starts now, regardless of your age. Turning 67, 68, or 70 without Medigap doesn't automatically mean you've missed your window; it depends on when you actually enroll in Part B, not when you turned 65.
What can close this window is having already used it — the federal Medigap Open Enrollment Period is generally a one-time opportunity tied to your first Part B enrollment. If you're outside that window and don't have a specific guaranteed-issue right or qualifying event, insurers can typically use medical underwriting to evaluate a new Medigap application. Some states add extra protections beyond the federal minimum, so it's worth confirming your specific situation with a licensed agent rather than assuming either way.
Coordinating Coverage
In most cases, yes — and the timing matters. Employer coverage that was based on active employment generally stops counting as a reason to delay Part B once that employment (or the coverage itself) ends. Enrolling in Medicare before your employer coverage actually ends, where possible, helps avoid a gap between the two. Waiting too long after coverage ends risks both a coverage gap and a permanent Part B late-enrollment penalty.
A High-Risk Mistake
Generally, no — and this is one of the costliest mistakes people make when retiring after 65.
COBRA is not considered coverage based on active employment, so it does not count the same way employer group coverage does, and it does not extend your 8-month Part B Special Enrollment Period. Many people assume COBRA buys them more time and enroll in Medicare late as a result — which can mean a coverage gap, a permanent Part B late-enrollment penalty, and a delayed Medigap Open Enrollment window.
If you're choosing between COBRA and Medicare as you retire, it's worth confirming your specific enrollment deadline before making a decision rather than assuming COBRA is a safe bridge.
Retiring Soon?
We'll help you work through when your employer coverage ends, when Medicare begins, and what Medicare Supplement and prescription coverage options are available to you.
No obligation. One-on-one help with a licensed Medicare advisor.
Purchase Decision
A carrier can explain its own plans. An independent Medicare agency can help you compare the companies and plan options available through the agency — which matters because, in most states, Medigap benefits are standardized by plan letter, but the premium, discounts, and rate history behind that letter can differ significantly from one company to the next.
Broader, more predictable coverage. You pay the annual Part B deductible; the plan generally helps with most other Medicare-covered cost-sharing.
Explore Plan GCan carry a lower premium in exchange for small office-visit and ER copays, and no coverage for Part B excess charges.
Explore Plan NPricing
There's no single national price, because several factors affect your personal premium:
For example, in our own review of Bethlehem, PA-area rates for a 65-year-old non-tobacco applicant, sample Plan G premiums ranged from roughly $125 to $269 per month depending on the insurance company — for the exact same standardized benefits. See the full Bethlehem rate comparison →
Prescription Coverage
Usually, yes. Medigap plans don't include prescription drug coverage, so most people pair a Supplement with a standalone Part D plan. This matters even more when you're retiring, since you're also losing whatever prescription coverage your employer plan provided. If you go 63 or more consecutive days without Part D or other creditable drug coverage after your Initial Enrollment Period, Medicare can add a late-enrollment penalty to your monthly Part D premium for as long as you have Part D coverage — so it's worth confirming in writing whether your employer's drug coverage was considered "creditable" before you assume you're covered in the meantime.
Paperwork
These are official CMS forms, filed with Social Security. We're not a substitute for Social Security's own guidance — a licensed agent can help you understand the process, but Social Security processes the Part B enrollment itself.
Plan Ahead
There's no official countdown for this, so here's the timeline we walk clients through:
Get your last day of active employment and your employer coverage end date in writing — your SEP starts whichever comes first.
File CMS-40B and CMS-L564, and begin comparing Original Medicare + Medigap against Medicare Advantage.
Choose Medigap or Medicare Advantage, add Part D if needed, and confirm every effective date lines up.
Employer coverage ends and your new Medicare coverage begins — no gap, no overlap.
Why Work With Us
Medicare.gov is an excellent source for official rules and for viewing available Medigap policies in your area. What Lehigh Partners adds is one-on-one guidance: helping you coordinate your retirement dates, compare the companies available through our agency, and complete the coverage transition. We're an independent Medicare agency, physically based in Bethlehem, PA — not a single carrier's call center.
Common Questions
A licensed Lehigh Partners Senior Benefits advisor can help you work through when your employer coverage ends, when Medicare begins, and what Medicare Supplement and prescription coverage options are available to you.
No cost to you. No obligation to enroll.
You pay the exact same premium whether you apply directly with a carrier or use our services.
Disclosure
Lehigh Partners Senior Benefits is a licensed insurance agency and is not connected with or endorsed by the United States government or the federal Medicare program. We do not offer every plan available in your area. We represent selected insurance organizations and products in the areas we serve. Contact Medicare.gov, 1-800-MEDICARE, or the Social Security Administration for official enrollment guidance and information about all available options. Enrollment periods, penalties, coordination-of-benefits rules, guaranteed-issue rights, and state protections vary by individual circumstance and state. This page provides general educational information and is not a substitute for advice based on your specific situation.
