More Americans than ever are still on the job at 65, which raises a question the Medicare program was not originally built around: what should someone do about Medicare while still covered by an employer health plan? The answer depends on the size of the employer, whether the coverage comes from active employment or something else like COBRA, and whether a health savings account is involved. Getting the sequence right can avoid late-enrollment penalties and coverage gaps; getting it wrong can create both. This 2026 guide walks through how Medicare while working past 65 actually works, in plain language, and where to confirm the rules for your own situation.
Turning 65 does not force you off employer coverage
A common misconception is that reaching 65 means leaving an employer plan. In reality, people with coverage through their own or a spouse’s active employment can generally keep that coverage, and Medicare enrollment becomes a coordination question rather than a replacement question. The key concept is which payer is “primary” — the one that pays claims first — and which is “secondary.” For people covered through active employment at a larger employer, the employer plan typically pays first and Medicare, if enrolled, pays second. For people at smaller employers, the order usually flips, and that flip changes what enrolling in Medicare on time actually protects.
The 20-employee rule concept
The dividing line most people encounter is employer size. When an employer has 20 or more employees, its group health plan generally remains the primary payer for an active employee who turns 65, and Medicare would pay second. Because the employer plan is primary, that coverage counts as what the rules treat as qualifying current-employment coverage, and many people in this position choose to delay Part B while they keep working, since Part B carries a monthly premium and would only supplement the employer plan.
When an employer has fewer than 20 employees, the arrangement generally reverses: Medicare becomes the primary payer once you are eligible, and the small-employer plan pays second. That means claims can be processed as though Medicare paid first even if you never enrolled, leaving significant gaps if Part A and Part B are not in place. People working for small employers are therefore usually told to enroll in Medicare during their Initial Enrollment Period rather than delay. Some small-employer plans have their own rules about Medicare-eligible employees, so it is worth asking the benefits administrator directly how the plan coordinates with Medicare before deciding anything.
Delaying Part B without penalty
Part B has a late-enrollment penalty that adds a percentage to the monthly premium for each full year of delay and generally lasts for as long as you have Part B. The important exception: months in which you were covered by a group health plan based on your own or your spouse’s current employment do not count toward the penalty. This is why an employee at a larger firm can delay Part B for years without consequence, then enroll when the job ends. The word “current” is doing real work in that sentence — retiree coverage, COBRA, and severance-period coverage are not based on current employment, so they do not provide the same protection. Many people in this situation still enroll in premium-free Part A at 65 since it can pay secondary to the employer plan, though there is one significant exception involving health savings accounts, covered below.
The COBRA caveat
COBRA is where careful plans often go wrong. COBRA lets people continue an employer’s health plan for a limited time after leaving a job, and it can look like a seamless bridge to a later Medicare start date. But for Medicare purposes, COBRA is not coverage based on current employment. Months on COBRA count toward the Part B late-enrollment penalty, and — critically — the Special Enrollment Period for enrolling in Part B is tied to when the employment or the employment-based coverage ends, not when COBRA ends. Someone who rides COBRA for many months before enrolling can find the special window has closed, leaving the General Enrollment Period and a lasting penalty as the only path. There is also a coordination trap: once someone is eligible for Medicare, COBRA typically pays secondary to Medicare, so relying on COBRA alone can leave the primary-payer position empty. The widely repeated guidance from program administrators is to treat the end of active employment, not the end of COBRA, as the Medicare deadline.
HSA contributions and Medicare do not mix
Health savings accounts add another wrinkle. Federal tax rules do not allow HSA contributions during any month a person is enrolled in any part of Medicare, including premium-free Part A. Since Part A enrollment can be applied retroactively for people who sign up after 65 or who begin Social Security benefits, contributions made during a retroactive coverage period can create excess-contribution problems at tax time. People who want to keep contributing to an HSA while working past 65 generally delay all parts of Medicare, including Part A, and also delay claiming Social Security, since starting those benefits triggers automatic Part A enrollment. Money already in an HSA is unaffected — it can still be spent on qualified medical expenses, including certain Medicare premiums, after enrolling. The contribution rules and retroactivity details are technical enough that a conversation with a tax professional or benefits administrator before the transition is a common recommendation.
The Special Enrollment Period when work ends
When active employment or the employer coverage ends — whichever comes first — a Special Enrollment Period opens for Part B. It generally allows enrollment during employment-based coverage or within a window of several months after that employment or coverage ends, without a late-enrollment penalty. Signing up before the job actually ends, where possible, helps avoid a gap between the employer plan stopping and Medicare starting. The transition also starts related clocks: leaving employer drug coverage that counts as creditable opens a window to join a Part D plan without penalty, and enrolling in Part B at 65 or older starts the one-time six-month Medigap open enrollment window, during which supplement policies are generally available without medical underwriting. Because several deadlines begin at the same moment, many people map out the sequence a few months before retiring.
Comparing the two paths while still employed
Keeping employer coverage is not automatically the better move, even when it is allowed. Employer plans differ widely in premiums, deductibles, provider access, and drug coverage, and some employees find that enrolling in Medicare — possibly with a supplement or a Medicare Advantage plan — compares favorably to their share of the employer premium. Relevant questions include what the employee’s share of the employer premium is, whether the employer plan’s drug coverage is creditable (employers are required to tell you each year), how dependents younger than 65 would be covered if the employee left the plan, and whether the employer offers any retiree coverage that coordinates with Medicare later. There is no single right answer; the point is that the comparison is worth making deliberately rather than by default.
How to verify the rules for your situation
Because the right move depends on employer size, coverage type, and HSA status, the safest approach is to verify your specific facts with the sources that administer the program. The interaction between employer coverage and Medicare, including the current-employment rules, is explained at Medicare.gov, and Part A and Part B enrollment itself is handled through the Social Security Administration at SSA.gov, which can also confirm how a Special Enrollment Period applies to you. Your employer’s benefits administrator can confirm the plan’s size classification and whether its drug coverage is creditable, and a State Health Insurance Assistance Program counselor or a licensed insurance agent can walk through the timing with you at no cost.
Final thoughts
Working past 65 with employer coverage is a well-worn path, and the rules accommodate it — but they hinge on details that are easy to miss. Coverage from current employment at a larger employer generally allows Part B to be delayed without penalty; small-employer coverage generally does not; COBRA never does; and HSA contributions require staying out of Medicare entirely, including Part A. When the job finally ends, a Special Enrollment Period opens, and several other windows start alongside it. Confirm your employer’s size and coverage rules, note which clock applies to you, and lean on Social Security, Medicare.gov, or a SHIP counselor before the transition rather than after.
Disclaimer
This article is for general informational purposes only and is not medical, financial, tax, legal, or enrollment advice. This site is not affiliated with or endorsed by Medicare, the Centers for Medicare & Medicaid Services, the Social Security Administration, or any government agency. Coordination rules, enrollment windows, penalties, and tax treatment can change and depend on individual circumstances. Always verify current information at Medicare.gov or with the Social Security Administration, and consider speaking with a licensed insurance agent, SHIP counselor, or tax professional before making enrollment decisions.