The numbers that matter
Your action plan
Here is the order I'd take if you were sitting in my office today.
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Confirm your employer size in writing
Ask your benefits administrator (or your spouse's) two questions: How many employees does the company have, and is the plan primary or secondary to Medicare? Get the answer in writing or in an email. Twenty employees is the line in the sand. Under 20 means Medicare is primary at 65 and you should enroll on time. Twenty or more usually means you can safely delay Part B until coverage ends.
Time: 15 minutes Cost: Free Medicare.gov: Working past 65
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Decide about Part A and your HSA
Part A is free for most people with 40 work credits, so it's tempting to grab it. But if you're contributing to a Health Savings Account, ANY part of Medicare disqualifies you from contributing — and Part A enrollment can be retroactive up to 6 months. Stop HSA contributions at least 6 months before applying. If you don't have an HSA, taking Part A as a secondary payer for hospital costs is usually fine.
Time: 30 minutes Cost: Free IRS Pub 969 (HSAs)
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File CMS-40B and CMS-L564 during your 8-month SEP
When your job ends or your group coverage ends — whichever comes first — you have 8 months to enroll in Part B without a Late Enrollment Penalty. File CMS-40B (your application) and CMS-L564 (employer attestation that your coverage was creditable). Submit to your local SSA office or by mail. Don't wait until the last week — apply about 3 months before you want coverage to start so SSA has time to process.
Time: 1 hour Cost: Free CMS-40B & CMS-L564 forms
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Get free, unbiased help — and ignore cold callers
Call your state SHIP at 1-877-839-2675 for free, unbiased counseling, or call Chapter at the number on this page for free help from licensed Medicare advisors. Tell them Dr. Ed sent you. One warning: if someone calls you to sell you a Medicare plan, hang up. Cold-call Medicare solicitation is prohibited under CMS marketing rules. Real help doesn't cold-call you.
Time: 30-60 minutes Cost: Free SHIP locator
Watch: Dr. Ed on working past 65
The 20-employee rule, in plain English
Short walkthrough on the size-of-employer rule, the 8-month Special Enrollment Period, and the HSA trap that catches people who enroll in Part A retroactively. (Video coming soon — in the meantime, read the FAQs below.)
Find your situation
Pick the line that sounds most like you. I cannot count the number of times the same five situations come up in the same week.
I work for a company with 20+ employees — can I delay Medicare?Usually yes — your employer plan stays primary.
Short answer: yes, you can usually delay Part B safely. With a 20+ employee employer, your group plan is primary and Medicare is secondary. You will get an 8-month Special Enrollment Period when you actually retire (or when group coverage ends, whichever is first). Use that window to file CMS-40B and CMS-L564.
Most people in this lane still take Part A at 65 because it's free with 40 work credits and acts as secondary coverage for hospital costs. The big exception is HSA contributors — see the HSA card below before you file.
If you want a second set of eyes, your state SHIP at 1-877-839-2675 will run the timing for free.
I work for a small employer (under 20) — what should I do?Enroll on time at 65. Medicare becomes primary.
If your employer has fewer than 20 employees, Medicare is primary at 65 and your group plan is secondary. That means if you don't enroll in Medicare, your group plan can refuse to pay the share Medicare would have paid. People learn this the hard way after a hospitalization.
Enroll in both Part A and Part B during your Initial Enrollment Period (the 7-month window around your 65th birthday). Your employer plan will coordinate with Medicare from there. If your employer plan is genuinely better than what Medicare offers, you can usually keep both — but you need Medicare in the primary slot.
If you also have an HSA, stop contributions before enrolling. See the HSA card.
My spouse has the employer coverage, not meSame rules apply through your spouse — size matters.
If you're 65 and not working, but you're covered as a dependent on your spouse's active group plan, you generally get the same SEP rights through your spouse's employment. The 20-employee rule still controls. If your spouse's employer has 20 or more employees, you can usually delay Part B and use an 8-month SEP when their employment ends or when you lose coverage.
If your spouse's employer has fewer than 20 employees, Medicare is primary for you at 65 — don't delay.
When your spouse retires, your SEP clock starts. File CMS-40B and ask their HR for the CMS-L564 attestation covering you as a dependent.
I contribute to an HSA — does Medicare affect that?Yes — enrolling in any part of Medicare ends HSA contributions.
This is the trap that catches more working-past-65 folks than anything else. Enrolling in ANY part of Medicare — even free Part A — makes you ineligible to contribute to an HSA from the month your Medicare starts. And here's the kicker: when you enroll in Part A after age 65, Medicare backdates your coverage up to 6 months (but never earlier than your 65th birthday).
If you keep contributing to your HSA into that retroactive window, the IRS treats those contributions as excess and charges a 6% excise tax per year via Form 5329 until you remove them.
The fix: stop HSA contributions at least 6 months before you apply for Medicare. If you're already past 65 and haven't enrolled, you can still contribute — but plan the wind-down carefully. IRS Pub 969 spells out the rules.
I'm retiring soon — when do I apply for Medicare?Apply about 3 months before your coverage ends.
The sweet spot is to file CMS-40B and CMS-L564 about 3 months before you want Medicare to start. SSA typically processes Part B applications within a few weeks, but pile-ups happen, and you don't want a coverage gap between your last day on the group plan and your Medicare start date.
Your 8-month SEP technically runs from the month your job ends (or coverage ends, whichever is first) through 8 months after — but waiting that long usually means a gap. Apply early, ask SSA for a coverage start date that lines up with the day after your group coverage ends.
A licensed Medicare advisor through Chapter or your state SHIP at 1-877-839-2675 can walk through the timing with you. Tell them Dr. Ed sent you.
I missed the SEP and now I'm on COBRACOBRA does not extend your SEP — act fast.
This is one of the most painful traps in Medicare. COBRA, retiree coverage, severance health benefits, and ACA marketplace plans do NOT count as active employer coverage and do NOT extend or trigger the 8-month Special Enrollment Period. Your SEP clock started the day you left active employment, not the day COBRA ends.
If you're still inside your 8-month window, file CMS-40B and CMS-L564 today. If the window has already closed, you'll have to wait for the General Enrollment Period (Jan 1 – Mar 31) and you may face a permanent Part B Late Enrollment Penalty of 10% per year you were eligible without enrolling.
Call SHIP at 1-877-839-2675 to map your dates. There are rare equitable-relief exceptions, but you have to ask.
I'm helping my parent who's still working at 65Three questions to ask before you do anything else.
If you're the adult child stepping in to help, ask three questions in this order:
1) How big is the employer? (Under 20 vs. 20+ changes everything.) 2) When does the parent plan to retire — do they have a target date? 3) Does the parent contribute to an HSA?
With those three answers in hand, call your state SHIP at 1-877-839-2675 together. SHIP counseling is free, unbiased, and not selling anything. They can walk through the SEP, the forms (CMS-40B and CMS-L564), and the HSA timing with you and your parent on the line.
One warning to pass along: if anyone calls your parent to sell them a Medicare plan, tell them to hang up. Cold-call Medicare solicitation is prohibited under CMS marketing rules. Real help — SHIP, Chapter, SSA — doesn't cold-call you.
My situation is different from theseGet free, individualized help — SHIP or Chapter.
Working past 65 is one of those areas where every situation has a wrinkle — a tribal employer, federal service, a foreign employer, an LLC where you're the only employee, a TRICARE overlap. The rules can be answered, but you need someone to walk through them with you.
Two good options, both free: your state SHIP at 1-877-839-2675 (free, unbiased counseling, no plans for sale), or Chapter (free help from licensed Medicare advisors, tell them Dr. Ed sent you).
Don't take advice from someone who cold-called you about Medicare. Cold-call Medicare solicitation is prohibited under CMS marketing rules.
Questions I get asked every week
Should I sign up for Medicare if I'm still working at 65?
It depends on the size of your employer (or your spouse's). If the employer has 20 or more employees, the group plan is primary at 65 and you can usually delay Part B safely — you'll get an 8-month Special Enrollment Period when active employment or coverage ends. If the employer has fewer than 20 employees, Medicare becomes primary at 65 and you should enroll on time. In all cases, talk to your benefits administrator and confirm in writing whether the plan is primary or secondary.
What's the 20-employee rule?
Federal law uses 20 employees as the line for Medicare Secondary Payer rules. With 20 or more employees, the group health plan is primary for active workers and their spouses age 65+. Under 20, Medicare is primary at 65, and the group plan pays as if Medicare had paid, even if you didn't enroll. That's why a 19-employee firm and a 20-employee firm are wildly different planets when it comes to Medicare timing.
What's the 8-month Special Enrollment Period?
The Part B Special Enrollment Period (SEP) is an 8-month window that starts the month after active employment ends OR the month after group coverage ends — whichever comes first. During the SEP you can enroll in Part A and/or Part B without a Late Enrollment Penalty. The legal basis is 42 CFR 407.20 for Part B and 42 CFR 406.27 for Part A, and SSA staff use POMS HI 00805.295 to administer it.
What forms do I need to enroll using my SEP?
Two forms. CMS-40B is your application for Part B. CMS-L564 is the employer attestation that confirms you had creditable group coverage during the period you're claiming. Your employer's HR signs the L564. Submit both to your local SSA office or by mail. SSA will sometimes accept a letter from the employer in lieu of CMS-L564, but the form is cleaner.
Will my employer plan stay primary?
If the employer has 20 or more employees AND you (or your spouse) are still actively working there, yes — the group plan is primary, Medicare is secondary. Once active employment ends, that primary status ends too, even if you keep the plan through COBRA or retiree coverage. After active employment, Medicare becomes primary. Filing the COB form (CMS-1763) helps your insurer coordinate correctly.
What about my Health Savings Account?
Enrolling in any part of Medicare ends your HSA eligibility starting that month. The trap is that Part A enrollment after 65 is retroactive up to 6 months (never earlier than your 65th birthday). HSA contributions made during that retroactive window become excess contributions, subject to a 6% IRS excise tax per year via Form 5329 until removed. The clean fix: stop HSA contributions at least 6 months before you apply for Medicare. The legal basis is 26 USC § 223 and IRS Pub 969.
Should I take Part A even if I delay Part B?
If you have 40 quarters of Medicare-taxed work (10 years), Part A is premium-free and acts as secondary coverage for hospital stays, which can lower your out-of-pocket costs. Most working-past-65 people in large-employer plans take Part A and delay Part B. The big exception is HSA contributors — if you're contributing to an HSA, taking even free Part A ends those contributions. Decide that piece first.
What if my spouse is the one with employer coverage?
If you're 65, not working, and covered as a dependent on your spouse's active group plan, your SEP rights flow through their employment. The 20-employee rule still controls. When your spouse retires or loses coverage, your 8-month SEP clock starts. Get a CMS-L564 from your spouse's employer covering you as a dependent. Same forms, same deadlines.
What if I miss the SEP?
If you miss the 8-month SEP, you'll have to wait for the General Enrollment Period (January 1 – March 31) and you'll likely face a permanent Part B Late Enrollment Penalty of 10% of the standard premium for every full 12 months you were eligible without enrolling. There are rare equitable-relief exceptions — if a Medicare or SSA representative gave you incorrect information, document it and request equitable relief through SSA. Don't assume you're stuck without asking.
Where can I get free help deciding?
Two free options. Your state SHIP at 1-877-839-2675 gives free, unbiased counseling — they don't sell plans and they don't take commissions. Or call Chapter for free plan comparison from licensed Medicare advisors; tell them Dr. Ed sent you. Both options will walk through your SEP timing, your spouse's coverage, your HSA, and your retirement date with you.
Related programs and pages
These pages travel together. If you're working past 65, odds are at least two of them apply to you.
Medicare Late Enrollment Penalty
What the penalty is, who pays it, and the rare ways out.
COBRA and Medicare
Why COBRA does not extend your 8-month SEP — and what to do instead.
Medicare Annual Enrollment Period
October 15 to December 7 — when you can change Medicare plans.
IRMAA: High-Income Medicare Surcharge
How retirement income affects what you pay for Part B and Part D.
Medicare Savings Program (MSP)
If your retirement income is modest, your state can pay your Part B premium.
Working While Collecting Social Security
How wages interact with your Social Security check before full retirement age.
Get the working-past-65 checklist
I'll send you a one-page checklist with the SEP dates, the two forms (CMS-L564 and CMS-40B), and the HSA timing. No spam, no plan sales pitches.
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