Working Past 65 in California: Do You Need Medicare Yet?

Turning 65 no longer means retiring. Many Californians keep working — and keep their employer health plan — well into their late 60s or 70s. The good news is that Medicare's rules allow for this. The catch is that the right move depends on details specific to your situation, and a wrong assumption can create a lifelong penalty or a coverage gap. This guide walks through how to think about it.

The key question: how big is the employer?

Almost everything about working past 65 comes down to the size of the employer providing your coverage — yours, or your spouse's, if you're on their plan through their current job.

Employers with 20 or more employees

If the coverage comes from current employment at an employer with 20 or more employees, the group health plan generally stays your primary coverage and Medicare would be secondary. In this situation, you can delay enrolling in Part B without a late-enrollment penalty for as long as that coverage continues. When the job or the coverage ends, a Special Enrollment Period lets you enroll then — penalty-free.

Employers with fewer than 20 employees

If the employer has fewer than 20 employees, Medicare generally becomes the primary payer once you turn 65, and the group plan pays secondary. That distinction matters a great deal: if you don't enroll in Part A and Part B on time, the plan may pay as though Medicare already covered its share — leaving you responsible for large bills. In these cases you usually should enroll in Medicare at 65. Always confirm how your specific plan coordinates with Medicare with your benefits administrator before deciding.

What about premium-free Part A?

Most people qualify for premium-free Part A (hospital insurance) at 65 based on their work history. Because it usually costs nothing, many people enroll in Part A at 65 even while still working, where it can pay secondary to the employer plan.

There is one important exception: Health Savings Accounts (HSAs). Enrolling in any part of Medicare — including premium-free Part A — ends your eligibility to contribute to an HSA. You can still spend down an existing HSA, but new contributions must stop. If continuing to fund your HSA matters to you, you may want to delay Part A along with Part B.

Don't forget Part D (drug coverage)

To avoid a permanent Part D late-enrollment penalty, you need creditable prescription drug coverage — coverage at least as good as Medicare's — with no gap of 63 days or more. Most large employer plans are creditable, and your plan is required to send you an annual notice stating whether its drug coverage is creditable. Keep those notices; you may need to show them later when you enroll in a Part D or Medicare Advantage plan.

A quick decision guide

• Large employer (20+), want to keep your HSA: You can generally delay all of Medicare, including Part A, while covered. Plan your HSA cutoff before enrolling later.
• Large employer (20+), no HSA: Many people take premium-free Part A at 65 and delay Part B until the job ends. No penalty for delaying Part B while covered.
• Small employer (under 20): Medicare is usually primary at 65 — enrolling in Part A and Part B on time is typically important. Verify with your benefits administrator.
• On a spouse's plan: The same size rules apply, based on the employer providing that coverage and whether it's from current employment.

Coverage rules can hinge on plan-specific language, so treat this as a framework — not a final answer for your exact plan.

When you do retire: the transition

Whenever you decide to stop working — or your employer coverage ends — you move into a Special Enrollment Period (SEP): 8 months to enroll in Part B without penalty, and 2 months to pick up a Medicare Advantage or Part D plan. Enrolling before your employer coverage ends is the cleanest path, with no gap. Two things trip people up: COBRA and retiree coverage do not count as current-employer coverage, so they don't extend this window. For a full step-by-step walkthrough of that handoff, see our companion guide, Retiring after 65: moving from employer coverage to Medicare in California.

How the plan choice works once you enroll

When you do come onto Medicare, you'll choose between the two main approaches — a Medicare Advantage plan, or Original Medicare paired with a Medigap policy and a Part D drug plan. We compare them in Medicare Advantage vs. Medicare Supplement, and our Medicare costs explained guide breaks down the 2026 numbers. If you go the Medigap route, the California Birthday Rule gives California Medigap policyholders an annual window, beginning on their birthday, to switch to a plan with equal or lesser benefits without medical underwriting. If you're closer to 65 than to retirement, the Turning 65 in Southern California overview and our step-by-step turning 65 guide are good starting points.

Frequently asked questions

Do I need Medicare at 65 if I have employer insurance?

It depends on your employer's size. If your (or your spouse's) current employer has 20 or more employees, the group plan generally stays primary and you can delay Part B without penalty while that coverage continues. If the employer has fewer than 20 employees, Medicare usually becomes primary at 65, so you generally need to enroll in Part A and Part B on time — confirm with your benefits administrator.

Should I take premium-free Part A while still working?

Many people do, because Part A is usually premium-free and can pay secondary to an employer plan. The main exception is if you contribute to a Health Savings Account (HSA): enrolling in any part of Medicare, including premium-free Part A, ends your eligibility to contribute to an HSA. If you want to keep contributing, you may choose to delay Part A.

Can I keep contributing to my HSA after 65 if I delay Medicare?

Yes, but only if you delay all of Medicare, including premium-free Part A. Because Part A can be backdated up to 6 months when you eventually enroll (never before age 65), a common approach is to stop HSA contributions at least 6 months before you plan to start Medicare to avoid a tax penalty. Confirm your timing with a tax advisor.

What happens to my Medicare enrollment when I finally retire?

When your current employment or the coverage tied to it ends, you get an 8-month Special Enrollment Period to sign up for Part B without a late penalty, plus 2 months for a Medicare Advantage or Part D plan. Enroll before your employer coverage ends to avoid a gap. COBRA and retiree coverage do not count as current-employer coverage and do not extend this window.

Where can I get free help in Southern California?

Contact Medicare.gov or 1-800-MEDICARE, get free unbiased counseling from California's Health Insurance Counseling & Advocacy Program (HICAP), which is California's State Health Insurance Assistance Program (SHIP), at 1-800-434-0222, or work with an independent licensed insurance agent at no cost to you.