Still Working at 65: What to Check Before You Delay Part B

Working past 65 can let some people delay Part B without penalty — but only when the coverage qualifies. The wrong assumption here is expensive and permanent.

If you are turning 65 and still working with active employer coverage, you may be able to delay Part B without a late enrollment penalty. The key word is active. COBRA is not active coverage for this purpose. Retiree coverage is not active coverage for this purpose. Even active employer coverage only protects you from the Part B penalty if the employer meets the size threshold (generally 20 or more employees for those 65 and over). Before delaying Part B, verify in writing — with your employer’s benefits team and Social Security — that your coverage qualifies. The penalty for getting this wrong can follow you for life.

This is the timing decision people most often get wrong. The cost of getting it wrong is permanent. Slowing down here is not optional — it is the work.

The short answer

If you have active employer group health coverage through current employment (yours or your spouse’s) at an employer with 20 or more employees, you can generally delay Part B without a late enrollment penalty. (Medicare.gov — Working Past 65)

When that coverage ends — meaning the employment ends or the qualifying coverage ends — you get an 8-month Special Enrollment Period to enroll in Part B without penalty. See The 8-Month Part B Special Enrollment Period.

If any part of that does not apply to you — for example, you have COBRA, retiree coverage, or your employer has fewer than 20 employees — the delay rules may be different, and a Part B late enrollment penalty may apply if you do not enroll on time.

How this applies to you

If you have active employer group coverage at an employer with 20+ employees: You may be able to delay Part B. Verify in writing.

If you have active employer group coverage at an employer with fewer than 20 employees: Medicare typically pays primary at 65. Most people in this situation enroll in Part B at 65 even while working. Verify with your employer’s benefits team.

If you have COBRA: COBRA is not active employer coverage for Part B timing. COBRA does not extend your Part B Special Enrollment Period. See COBRA and Medicare: Why the Timing Is Different.

If you have retiree coverage: Retiree coverage is not active employer coverage. The Part B SEP based on active employment does not apply. See Retiree Coverage Is Not Always Active Employer Coverage.

If you are covered through your working spouse: The same rules generally apply — if your spouse’s employer has 20+ employees and the coverage is active, you may be able to delay Part B. Verify both your spouse’s employer size and the plan’s interaction with Medicare.

If you are turning 65 and still working: Start with the broader picture in Turning 65? Start With Timing, Not Plans, then come back here for the specific Part B question.

The employer-size test

The 20-employee threshold matters because of how Medicare coordinates with employer coverage:

• Employer with 20 or more employees: Employer coverage is generally primary; Medicare is secondary. You may delay Part B without penalty while the active coverage continues.
• Employer with fewer than 20 employees: Medicare is generally primary at 65; the employer plan is secondary. If you do not enroll in Part B, the employer plan may not cover what Medicare would have paid — leaving you with bills the plan will not pick up.

This is one of the most consequential tests in Medicare timing. The size threshold is set in federal Medicare Secondary Payer rules, but how a specific employer plan handles it depends on the plan’s documents. (CMS — Medicare Secondary Payer)

Verify the employer size and the plan’s coordination rules in writing before delaying Part B.

What “active” means

For Part B timing, “active” coverage means coverage from current employment — yours or your spouse’s. The moment the employment ends, the coverage stops being “active” for Part B SEP purposes, even if COBRA or retiree coverage continues afterward.

• Employment ends → active coverage ends → 8-month SEP starts.
• COBRA does not extend “active” status.
• Retiree coverage does not extend “active” status.
• A leave of absence may or may not — depends on the employer and the leave type. Verify.

What people often get wrong

• ”COBRA is just employer coverage that keeps going.” For purposes of paying medical bills, COBRA may feel like employer coverage. For Part B timing, it is not. The 8-month SEP clock generally starts when active employment or the qualifying employer coverage ends, not when COBRA ends. Verify with Social Security.
• ”My retiree coverage will protect me from the penalty.” Retiree coverage is valuable, but it does not qualify as active employer coverage for the Part B SEP. Most retirees need to enroll in Part B on time even if retiree coverage continues.
• ”My employer’s HR said I do not need Part B.” Some HR departments are accurate; some are not. Get the specific guidance in writing. Confirm with Social Security separately. The cost of being wrong here is paid in higher Part B premiums for the rest of your life.
• ”The penalty is small.” The Part B late enrollment penalty is 10% of the Part B premium for each full 12-month period you could have had Part B but did not — and you pay that increased premium for as long as you have Part B. Over a 20-year retirement, that adds up. (Medicare.gov — Part B Late Enrollment Penalty)

What to check before delaying Part B

1. Confirm employer size. Get it in writing from your employer’s benefits team.
2. Confirm the plan’s coordination with Medicare. Ask whether the plan pays primary or secondary at 65.
3. Confirm whether the plan provides creditable drug coverage. This affects whether you can also delay Part D without a separate penalty.
4. Confirm with Social Security. Call Social Security or use SSA.gov. They make the official enrollment determination.
5. Get the answers in writing. “I was told over the phone” is not enough if the determination is later disputed.
6. Plan ahead for the 8-month SEP. Know the date your employment or qualifying coverage ends. That date starts the clock.

A simple timing prompt

”Is my current coverage active employer coverage from current employment, at an employer with 20 or more employees, in writing?”

If you cannot answer all three of those parts in writing, do not delay Part B based on assumption.

Slow is correct here. The verification is the work. Get it in writing, then decide.

This is a piece of a bigger picture

This article is part of Enrollment & Timing.