If you're still working at 65 and covered by an active employer group health plan, you can usually delay Part B without a late penalty and pick it up later through a Special Enrollment Period. Usually — because the answer swings on how many employees your company has, and on whether you contribute to an HSA. Get those two facts straight and the rest of the decision is fairly simple.
Before anything else, find out how many employees your employer has. Not roughly — actually. This single number decides which program pays your claims first, and everything downstream follows from it.
20 or more employees. The employer group plan generally pays first and Medicare pays second. Because you have creditable primary coverage from active employment, you can generally delay Part B without triggering the late-enrollment penalty, and you get a Special Enrollment Period when the job or the coverage ends. This is the common case, and it's the one people are thinking of when they say "you can wait."
Fewer than 20 employees. Now it flips: Medicare generally pays first and the group plan pays second. This is the scenario that quietly wrecks people. If you skip Part B here, the group plan may pay only the portion it would have paid as the secondary payer — leaving you responsible for the share Medicare would have covered, on claims you assumed were covered. Small-employer retirees have been handed five-figure bills over this.
Same-question caution for spouses: if you're covered through your spouse's active employment, the rule follows their employer's size, not yours.
You can't reason your way to this answer from the outside. Call your benefits administrator and ask two questions in these words: "Is this plan primary or secondary to Medicare for someone 65 or older?" and "Is this coverage creditable for Medicare Part B and Part D?" Ask for the answer in writing. Our employer coverage checker walks the same logic if you want to sanity-check what you're told.
Most people with 10 or more years of Medicare-taxed work pay no premium for Part A. When something is free and it can only add hospital coverage on top of what you already have, the default answer is take it. For most people still working, that default holds.
There is one significant exception, and it catches high earners and small-business owners constantly: if you're enrolled in Medicare — including premium-free Part A alone — you can no longer contribute to a Health Savings Account. Not reduced. Stopped.
Worse, there's a lookback most people never hear about. When you eventually enroll in Part A after 65, coverage is generally made retroactive up to six months (never earlier than the month you turned 65). Contributions you made during those retroactive months become excess contributions, with tax consequences attached. The practical rule people in this position use: stop HSA contributions about six months before the month your Medicare will start.
To be precise about what's involved: this is your money and your tax return, so the actual planning conversation belongs with your tax adviser. What I want you to leave with is that the HSA question exists and has to be answered before you file for Part A — not after.
One more small trap in the same neighborhood: if you're already drawing Social Security benefits at 65, you're generally enrolled in Part A automatically and you cannot decline it while keeping those benefits. If preserving HSA contributions matters to you, that interaction is worth mapping before you claim Social Security.
The protection above comes from being covered by a plan tied to current, active employment — yours or your spouse's. Several things that feel like employer coverage do not qualify, and the distinction is expensive:
I'd put this at the top of the list of the most costly misunderstandings in all of Medicare. Someone retires at 64, takes 18 months of COBRA believing it protects them, and arrives at Part B enrollment with penalty months already accrued and their Special Enrollment Period counted from the wrong date. The Medicare penalty calculator will show you what a stretch of missed months actually costs — the Part B penalty is 10% of the premium for each full 12-month period you could have had it and didn't, and it lasts for as long as you have Part B.
Part D has its own version: 1% of the national base premium ($38.99 in 2026) for each month you go without creditable drug coverage, also permanent. If your employer plan's drug coverage is creditable, you're fine — which is exactly why that second question to your benefits administrator matters.
When active employment or the group coverage ends — whichever happens first — a Special Enrollment Period opens:
Paperwork note that saves real grief: enrolling through this Special Enrollment Period generally requires your employer to complete a form (CMS-L564) confirming your dates of coverage. Employers are sometimes slow with it and HR contacts move on. Request it early, and don't wait until month seven of eight.
If you're approaching 65 and plan to keep working, do these in this sequence:
Two facts and a calendar entry, essentially. When people get burned on this, it's almost never because the rules were too complex — it's because nobody told them the small-employer flip or the COBRA gap existed. The full picture of how the parts fit together is in the 2026 Medicare guide, and how to apply for Medicare covers the mechanics when your time comes.
If you want a second opinion on your specific situation — employer size, spouse's coverage, an HSA in the mix — that's a free conversation with no obligation to enroll in anything: (561) 660-9102.
Required disclosures: Smooth Health Solutions 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. Currently we represent 0–78 organizations which offer 0–2,613 products in your area. The exact number of organizations and products depends on your ZIP code, county, and plan year. Please contact Medicare.gov, 1‑800‑MEDICARE, or your local State Health Insurance Assistance Program (SHIP) to get information on all of your options. This article is educational — it explains how Medicare timing works alongside employer coverage, not any specific plan.
Not necessarily. If you're covered by an active employer group plan — yours or your spouse's — at an employer with 20 or more employees, you can generally delay Part B without penalty and enroll later through a Special Enrollment Period. At employers with fewer than 20 employees, Medicare is usually the primary payer and delaying Part B can leave you exposed. Confirm your employer's size and whether the plan is primary or secondary before deciding.
For most people, yes — it costs nothing and can only add coverage. The exception is anyone contributing to a Health Savings Account: enrolling in Medicare, including premium-free Part A, ends HSA contribution eligibility, and Part A enrollment after 65 is generally made retroactive up to six months. Talk to your tax adviser before enrolling if an HSA is involved.
No. COBRA is continuation coverage after employment has ended, so it does not protect you from the Part B late-enrollment penalty, and your 8-month Special Enrollment Period generally runs from when the employment or group coverage ended — not from when COBRA ends. This is one of the most expensive misunderstandings in Medicare.
Generally 8 months, starting the month after employment ends or the month after the group health coverage ends, whichever comes first. Part D is much shorter — about 2 months (63 days) after creditable drug coverage ends. Enrolling through this window usually requires form CMS-L564 completed by your employer, so request it early.
10% of the premium for each full 12-month period you could have had Part B but didn't, and it applies for as long as you have Part B. Miss two years and you're paying roughly 20% extra for life. The penalty calculator will run your own numbers.
It can. Coverage through a spouse's active employment generally counts the same way your own would — but the employer-size rule follows their employer, not yours. Ask their benefits administrator whether the plan is primary or secondary to Medicare for a covered spouse aged 65 or older, and get it in writing.
Plans differ by carrier, county, and income. I'll check the actual 2026 plans where you live — free, in about 10 minutes, no pressure.
No cost. No pressure. No obligation to enroll.
Free tools and guides — no phone number required:
Important: This article is general information, not insurance, legal, tax, or medical advice. Coverage details vary by plan, carrier, state, and county, and change over time — always confirm benefits with the specific plan documents or a licensed agent before making decisions. Smooth Health Solutions is not connected with or endorsed by the U.S. government, the federal Medicare program, CMS, HealthCare.gov, or any state marketplace or government agency.