Working Past 65: When Medicare and Employer Coverage Overlap

If you or your spouse still work at 65 and have health coverage through that current employer, you may be able to delay Medicare Part B without a late enrollment penalty. The employer's size decides whether that job-based coverage pays first or whether Medicare does, and that answer changes what you should sign up for and when.

This is one of the few Medicare decisions where acting early can cost you money and acting late can also cost you money. The rules differ by employer size, by whether the coverage is based on current employment, and by which part of Medicare you are considering. Each of those is a separate question with its own answer.

The 20-employee rule decides who pays first

When you have Medicare and group health coverage from a current employer, Medicare uses a size test to set the order of payment. The 2027 Medicare handbook's coordination chart states it plainly for people 65 or older with coverage from their own or a spouse's current place of work:

Your situation	Medicare pays first	Other insurance pays first
Employer has fewer than 20 employees	Yes
Employer has fewer than 20 employees but participates in a multi-employer plan with 20 or more employees total		Yes
Employer has 20 or more employees		Yes

Source: Medicare & You 2027, coordination of benefits chart. The threshold count comes from the employer, and the multi-employer row means the answer is not always the number on your own pay stub.

Why this matters practically: if the employer plan pays first, it is primary and Medicare is secondary, so you can often wait on Part B. If Medicare pays first, the employer plan is secondary and may pay less than you expect, and it may require you to have Part B before it pays anything. Medicare warns on the same page that if your group health plan or retiree health coverage is the secondary payer, you will likely need to sign up for Part B before your insurance will pay.

The small-employer branch is stated directly on Medicare's signup page: because the company has fewer than 20 employees, your job-based coverage might not pay for health services if you don't have both Part A and Part B. That is a real financial exposure, not a technicality.

Whether you can delay Part B at all

Size is only half the test. The other half is whether the coverage is based on current employment, which is the phrase Medicare uses to describe coverage from an employer you or your spouse still work for.

If it is, you can sign up for Part A and Part B during a Special Enrollment Period: any time you are still covered by the group health plan, or during the 8-month period that begins the month after the employment ends or the coverage ends, whichever happens first. You will generally avoid a late enrollment penalty if you enroll in that window.

Two conditions sit inside that sentence and both are easy to misread. The clock starts at whichever event happens first, not last. And the window is measured in months after that event, so the practical deadline arrives earlier than a reader counting from a retirement party might expect.

Part A is usually a different decision from Part B. Most people qualify for premium-free Part A, and the handbook suggests signing up for Part A at 65 even if you keep working, because you may want to sign up for Part A when you turn 65, even if you or your spouse are still working. Part A has no premium in that case, and having it does not disturb your employer coverage. Part B is where the premium is, and where the delay decision actually lives.

Part D and drug coverage use a different clock

The Part B eight-month window does not apply to drug coverage. Medicare states that leaving employer or union coverage, including COBRA, generally gives you two full months after the month coverage ends to join a Medicare Advantage or drug plan.

The protection while you are still working comes from a different concept: creditable coverage. As long as your employer drug coverage is creditable, meaning it is expected to pay, on average, at least as much as Medicare drug coverage, you can wait to join a drug plan without a penalty.

Your plan has to tell you whether its coverage is creditable, and it must send that information every year. Keep those notices. If a new plan asks whether you had creditable coverage, that documentation is your answer, and reconstructing it years later is difficult. Medicare's working-past-65 page puts the instruction simply: keep the information your current drug plan sends, because you may need it when you are ready to join a Medicare drug plan, and notes you should not send it to Medicare.

The gap test is separate from the enrollment window. Going 63 or more consecutive days without creditable drug coverage after your initial enrollment period can trigger a Part D penalty even if an enrollment opportunity is still open. Our Part D coverage guide explains how that penalty is calculated.

The HSA interaction that surprises people

A Health Savings Account requires that you not be enrolled in Medicare. The handbook states that you aren't eligible to make contributions to an HSA after you have Medicare.

The trap is retroactivity. Premium-free Part A coverage will go back retroactively 6 months from when you sign up for Part A or apply for benefits from Social Security or the Railroad Retirement Board, but no earlier than the first month you were eligible for Medicare. So a contribution you made in the months before applying can turn out to be an ineligible contribution after the fact, which carries a tax consequence.

Medicare's working-past-65 page gives the practical rule: if you have a Health Savings Account, you and your employer should stop contributing to your HSA 6 months before you retire or apply for benefits. That advice is about avoiding a tax penalty, not about avoiding Medicare.

This is where the decision becomes genuinely two-sided. Someone with an employer high-deductible plan and an HSA may be better off delaying Part A as well as Part B, even though Part A is free, because taking Part A ends HSA eligibility. That is a tax decision as much as a Medicare one, and it depends on how much you and your employer contribute.

What COBRA does and does not do

COBRA is often mistaken for the coverage that lets you delay Medicare. It is not. The handbook is explicit: COBRA coverage isn't considered coverage based on current employment and doesn't count as current employer coverage to make you eligible for this Special Enrollment Period. It adds that the same is true for retiree health plans and VA coverage.

The practical consequence: if you are Medicare-eligible and take COBRA instead of Part B, COBRA coverage ending does not give you a penalty-free Part B window. You still have the 8-month period measured from when current employment or the employer coverage ended, whether or not you chose COBRA.

COBRA also pays poorly alongside Medicare for someone who is eligible. The handbook notes that if you have COBRA and you are eligible for Medicare, COBRA may only pay a small portion of your costs. Paying the full COBRA premium for secondary coverage is a bad trade for most people, and it is worth checking before you elect it.

Our COBRA or Marketplace guide covers the separate question of choosing between COBRA and an individual plan, which is a different decision from this one.

Retiree coverage and Marketplace coverage are separate tracks

Two other kinds of coverage show up in this conversation and behave differently from current-employment coverage.

Retiree coverage from a former employer is not coverage based on current employment, so it does not support delaying Part B on that basis. It also usually pays after Medicare. If you have retiree coverage, check with the plan before changing anything, because the handbook warns that if you have retiree coverage, don't risk losing it, and advises asking the employer whether joining a plan the employer does not offer would end it.

Marketplace coverage is the other case. Medicare is clear that you should sign up for Medicare when you are first eligible even if you have Marketplace coverage, and that once you are considered eligible for premium-free Part A, you will not qualify for Marketplace help with premiums. Continuing to take that help after Medicare eligibility can mean paying back some or all of it when you file your taxes. Marketplace coverage is not a substitute for the employer coverage exception.

Questions to settle before you decide

Work through these with your benefits administrator, not only with a plan brochure.

• How many employees does the employer have, and is it part of a multi-employer plan that changes the count? This sets the payment order.
• Is the coverage based on your or your spouse's current employment, as opposed to retiree or COBRA coverage? Only current-employment coverage supports the Part B delay.
• Does the plan require you to have Part B before it pays, or does it reduce benefits for people who are Medicare-eligible? Ask directly rather than inferring from the summary.
• Is the drug coverage creditable, and do you have the annual notice proving it? Keep every notice.
• Do you or your employer contribute to an HSA? If so, work out the last permissible contribution month before you apply for Part A or Social Security benefits.
• What is the exact date employment or coverage ends? The 8-month Part B clock and the 2-month drug plan clock start from that date, and they are not the same clock.

One timing detail from Medicare is worth putting on the calendar: if you want Medicare to start when your job-based coverage ends, sign up for Part B the month before you or your spouse plan to retire, because coverage starts the month after Social Security receives the completed forms.

If you are weighing when to enroll and how your employer plan fits with Medicare, ask NavaQuote about your Medicare options. Bring the employer's plan documents, the creditable coverage notice, your HSA contribution records, and the date your coverage ends. Our Medicare enrollment periods guide lays out the general windows, and our Advantage versus Supplement guide covers the coverage decision you will make once you enroll.