By Marc Gilman
Questions? Call (800) 927-9326 or email
Key Takeaways
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Check your employer’s size first. If your group health plan has fewer than 20 employees, Medicare generally pays primary — delaying Part B usually isn’t the right move at all, regardless of HSA or timing considerations.
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If you have an HSA and do qualify to delay Medicare, stop contributing at least 6 months before you apply — Medicare’s Part A retroactivity (up to 6 months back) can otherwise trigger a tax penalty.
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Medicare Advantage and Medicare Supplement (Medigap) are genuinely different products, not just different price points — deciding between them is the single biggest decision in this whole process.
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If you plan to enroll in Medigap, know your window: it’s a one-time, 6-month guaranteed issue period from your Part B start date at the federal level — but Massachusetts adds an annual Feb 1–Mar 31 window, while New Hampshire does not.
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COBRA, retiree coverage, VA coverage, and Marketplace coverage do NOT count as employer coverage for Special Enrollment Period purposes — your real SEP deadline is 8 months from when your job or group coverage ends, whichever comes first, and none of those alternatives extend it.
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If retiring changes your income, retiring itself can qualify as a “life-changing event” for an SSA-44 form, potentially lowering an IRMAA surcharge based on outdated income data.
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The right SEP forms matter: CMS-40B (Application for Enrollment in Part B) and CMS-L564 (Request for Employment Information) are what you’ll need if you’re not enrolling online.
8–9 Months Before Retiring
Find out how many employees your group health plan employer has — it determines your whole strategy. If your employer has fewer than 20 employees, Medicare generally pays primary, and delaying Part B usually isn’t advisable at all. The “delay and time it carefully” approach below applies specifically to people on a large group health plan (20+ employees), where the employer plan typically pays first.
If you do qualify to delay, confirm your Part A effective date and stop HSA contributions accordingly. If you’re enrolling in Medicare Part A after your Initial Enrollment Period, Medicare can make your Part A effective date retroactive up to 6 months from your application date — though never earlier than the first day of your 65th birthday month. To avoid a tax penalty, stop contributing to your HSA at least 6 months before you apply for Medicare, per Social Security’s own guidance — not just before your coverage technically starts.
Check whether IRMAA will apply to you, and whether SSA-44 might help. IRMAA (Income-Related Monthly Adjustment Amount) surcharges on Part B and Part D are based on your tax return from two years prior — which often reflects your pre-retirement income, not your actual retirement income. Retiring itself counts as a qualifying life-changing event for Form SSA-44, which can request a reassessment based on your current, lower income rather than waiting for the tax data to catch up.
6 Months Before Retiring
Learn the real difference between Medicare Advantage and Medicare Supplement. This isn’t just a cost comparison — Medicare Advantage plans use provider networks and often require referrals, while Medicare Supplement (Medigap) plans work alongside Original Medicare with broader provider access but a separate monthly premium. Get this decision right before your enrollment window opens, since switching later isn’t always guaranteed issue.
If you’re leaning toward Medigap, know your actual window — and that it’s not the same everywhere. The federal rule gives you a one-time, 6-month guaranteed issue window starting the month you’re 65+ and enrolled in Part B. Massachusetts goes further, offering an annual guaranteed issue window every February 1 through March 31, plus most MA insurers voluntarily accept new enrollees year-round. New Hampshire has no equivalent extra protection — the one 6-month window is genuinely your only guaranteed issue opportunity there, which makes timing it correctly the first time more important if you’re an NH resident.
Calculate your expected monthly premiums and real out-of-pocket costs. Add up your Part B premium (adjusted for IRMAA if it applies), your Part D or Medicare Advantage premium, and your Medigap premium if you’re going that route — then compare against your anticipated Rx and medical costs under each path.
2–3 Months Before Retiring
Know what actually counts as coverage that keeps your SEP window open — and what doesn’t. Your Special Enrollment Period lasts up to 8 months from the month your employment or group coverage ends, whichever happens first. But COBRA, retiree health coverage, VA coverage, and Marketplace/individual coverage do NOT count as coverage based on current employment — enrolling in any of those after leaving your job doesn’t extend your SEP window, even though it can feel like uninterrupted coverage. This is one of the most common and costly mix-ups in this whole process.
Enroll in Medicare Parts A and B. If you can, do this online through ssa.gov. If you’re enrolling through a Special Enrollment Period because you’re losing employer coverage, you’ll need two specific forms instead: CMS-40B (Application for Enrollment in Part B) and CMS-L564 (Request for Employment Information, which your employer partially completes to document your prior coverage). If your employer can’t complete Section B, you can fill out what you can yourself and submit secondary evidence instead — W-2s showing pre-tax medical contributions, pay stubs with premium deductions, or health insurance cards showing a policy effective date all work.
Check your enrollment status directly through ssa.gov rather than assuming your application went through — enrollment issues are far easier to fix before your coverage start date than after.
Enroll in a Part D plan, and your chosen Medigap or Medicare Advantage plan. If you identified an SSA-44 situation in the 8–9 month step, this is also a reasonable time to submit that form if you haven’t already, so the adjustment can take effect as close to your Medicare start date as possible.
The Month Before You Lose Employer Coverage
Confirm you have your official red, white, and blue Medicare card from CMS.
Confirm you have your Part D, Medigap, or Medicare Advantage plan ID cards — you’ll need these on file before your first appointment or prescription fill under the new coverage.
Cancel your employer coverage or COBRA only once your new coverage is confirmed active — canceling too early, before confirming your Medicare and supplemental coverage start dates line up, can create a gap that’s genuinely difficult to fix after the fact.
What To Do Next
Retiring onto Medicare involves more moving pieces than people expect — HSA timing, the Medicare Advantage vs. Medigap decision, state-specific enrollment windows, and IRMAA all intersect in the months leading up to your actual retirement date. Getting the sequence right the first time avoids coverage gaps and costly enrollment mistakes that are hard to undo later.
If you’re planning a retirement date and want to map out your specific timeline, reach out and we’ll build it with you.
Questions? Call (800) 927-9326 or email
