Working Past 65: Do You Need Medicare?
The Employer Size Rule
Medicare has a coordination-of-benefits rule that determines which insurance pays first.
Employers with 20+ employees: Your employer plan is "primary" — it pays first. You can delay enrolling in Medicare Part B without penalty. Most people in this situation choose to delay Part B (which has a monthly premium) and keep their employer coverage.
Employers with fewer than 20 employees: Medicare becomes primary at 65. If you don't enroll, your employer plan may refuse to pay — or pay as if Medicare had already covered its share. You can end up with large bills, and you'll face a permanent late enrollment penalty when you eventually sign up.
This same rule applies if you're covered under a spouse's employer plan. What matters is the employer's size, not whose plan you're on.
What Are Your Options at 65?
| Situation | Recommended Action |
|---|---|
| Employer has 20+ employees, you like your coverage | Enroll in Part A (free for most), delay Part B |
| Employer has fewer than 20 employees | Enroll in both Part A and Part B by your 65th birthday |
| High-deductible health plan with HSA | Consider delaying Part A too — Part A enrollment ends HSA contribution eligibility |
| Covered under spouse's employer (20+ employees) | Same rules apply based on spouse's employer size |
The Part A vs. Part B Decision
Part A (Hospital Insurance): Free for most people (40+ work quarters). Rarely a reason not to take it. Exception: if contributing to an HSA, enrolling in Part A ends your HSA eligibility.
Part B (Medical Insurance): $185/month in 2025 for most people. Delay if 20+ employer. Must enroll if small employer (under 20).
What Happens If You Delay Medicare and Shouldn't Have?
- Coverage gaps: Your employer insurer calculates what Medicare would have paid and covers only the remainder — leaving unexpected bills.
- Permanent Part B penalty: 10% per 12-month period you were eligible but didn't enroll. Added to your premium permanently — for life.
- Permanent Part D penalty: If you go more than 63 days without creditable drug coverage, a permanent penalty applies to Part D premiums.
Special Enrollment Period When You Retire
When you retire or lose employer coverage, you qualify for a Special Enrollment Period (SEP). You have 8 months to enroll in Part B without penalty starting from the month your employment or employer coverage ends (whichever comes first).
Frequently Asked Questions
Can I stay on my employer's plan past 65 instead of taking Medicare?
Yes, if your employer has 20 or more employees. Your employer coverage remains primary and you can delay Part B without penalty. Still take Part A — it's free for most people.
What if my employer has exactly 20 employees?
The threshold is "20 or more." An employer with exactly 20 employees qualifies. Under 20 (1–19 employees) means Medicare is primary.
Does the employer size rule apply to my spouse's employer?
Yes. If you're covered under your spouse's employer plan, the same rules apply based on your spouse's employer's size.
What is the Medicare Part B late enrollment penalty?
10% of the standard Part B premium for every 12-month period you were eligible but didn't enroll. It's added to your premium permanently — it never goes away.
I turned 65 and didn't enroll. What do I do now?
If you have qualifying employer coverage, you may still be within your initial enrollment window. If you've missed it, talk to a licensed advisor about Special Enrollment Period options. Match with an advisor