When Should I Sign Up for Medicare? - Plans Plus for Seniors Learn the 3 Medicare enrollment scenarios: turning 65, still working, and late enrollment.

Medicare enrollment is not one-size-fits-all. With over 67 million Americans currently enrolled, millions of people navigate this decision every year. The good news? There are really only three main enrollment scenarios, and once you understand which one applies to you, the path forward becomes crystal clear.

The bad news? Missing the right window can trigger lifetime penalties that permanently increase your premiums. Let’s walk through each scenario so you know exactly what to do and when.

Scenario 1: You’re Turning 65 and Retiring (or Already Retired)

This is the most straightforward scenario. You’re approaching your 65th birthday, you don’t have employer coverage (or you’re leaving it), and you need Medicare to be your primary health insurance.

Your Initial Enrollment Period (IEP)

Your IEP is a 7-month window centered around the month you turn 65:

3 months before your 65th birthday month
The month of your 65th birthday
3 months after your 65th birthday month

For example, if your birthday is in June, your IEP runs from March 1 through September 30.

What to Enroll In During Your IEP

Medicare Part A (Hospital Insurance) — Most people pay $0 in premiums if they or their spouse paid Medicare taxes for 10+ years. There’s no reason to delay.
Medicare Part B (Medical Insurance) — Covers doctor visits, outpatient services, and preventive care. The standard premium for 2026 is set by CMS each year. You’ll want this active by the time you lose other coverage.
Part D or Medicare Advantage — You’ll also need prescription drug coverage (Part D) unless you enroll in a Medicare Advantage plan that already includes it.

The Penalty You Don’t Want

If you miss your IEP and don’t qualify for a Special Enrollment Period (Scenario 2), you’ll face a Part B late enrollment penalty: your premium goes up 10% for every full 12-month period you could have had Part B but didn’t. This penalty lasts for the rest of your life.

Part D has a similar penalty: roughly 1% of the national base premium for every month you went without creditable drug coverage.

Pro Tip: Enroll Early in Your Window

If you enroll in the first three months of your IEP (before your birthday month), your coverage typically starts on the first day of your birthday month. If you wait until your birthday month or later, coverage can be delayed by 1–3 months.

Scenario 2: You’re Turning 65 but Still Working (With Employer Coverage)

This is where it gets nuanced. If you’re still working at 65 and have health insurance through your employer (or your spouse’s employer), you may not need to enroll in all parts of Medicare right away.

The Employer Size Rule

The key question: How many employees does the company have?

20 or more employees: Your employer plan is primary. Medicare is secondary. You can safely delay Part B (and Part D, if your employer drug coverage is “creditable”) without penalty.
Fewer than 20 employees: Medicare is primary. You should enroll in Part B during your IEP even if you have employer coverage, because the employer plan will pay second.

What You Should Still Do at 65

Even if you’re delaying Part B, most people should still sign up for Part A. It’s premium-free for most people and doesn’t interfere with employer coverage. The one exception: if you’re contributing to a Health Savings Account (HSA), enrolling in Part A will disqualify you from making HSA contributions.

When You Leave Employer Coverage

Once you retire or lose employer coverage, you get a Special Enrollment Period (SEP):

Special Enrollment Period Timeline

Part B: You have 8 months from the date your employment ends or your employer coverage ends (whichever comes first) to enroll without penalty.

Part D: You have 63 days from the date your creditable drug coverage ends to enroll without penalty.

Medigap: You have a 6-month open enrollment starting when your Part B becomes effective. During this window, insurance companies cannot deny you coverage or charge more due to pre-existing conditions.

This is critical: COBRA and retiree coverage do not count as employer coverage for the purpose of qualifying for a Special Enrollment Period. If you go on COBRA after leaving your job, your 8-month SEP clock started when your employment ended — not when COBRA ends.

Scenario 3: You Missed Your Enrollment Window

If you missed your Initial Enrollment Period and don’t qualify for a Special Enrollment Period, you’ll need to wait for the General Enrollment Period (GEP).

General Enrollment Period

The GEP runs January 1 – March 31 each year. If you enroll during the GEP, your Part B coverage starts July 1 of that year.

That means you could go several months without coverage, and you’ll owe the late enrollment penalty on top of your regular premium.

This is the scenario everyone wants to avoid. The combination of a coverage gap and permanent premium increases makes it the most expensive path to Medicare. If you think you might be in this situation, talk to a licensed broker who can review whether you qualify for any exceptions.

Which Scenario Are You?

Here’s a quick way to figure out your path:

Turning 65 with no employer coverage? → Scenario 1. Enroll during your IEP, ideally 3 months before your birthday month.
Turning 65 with employer coverage (20+ employees)? → Scenario 2. Sign up for Part A, delay Part B, and enroll within 8 months of leaving your job.
Already past 65 and missed the window? → Scenario 3. Enroll during the GEP (Jan 1 – Mar 31) and explore whether any exceptions apply.

Want the Full Picture?

Our free 16-chapter Medicare Roadmap covers enrollment, plan comparisons, costs, penalties, and more — all in plain English.

Download Free Guide →

Don’t Navigate This Alone

Medicare enrollment mistakes can cost you thousands over your lifetime, and they’re often irreversible. As independent brokers licensed in all 50 states, we work for you — not the insurance companies. We’ll walk you through which scenario applies, what to enroll in, and when to do it.

Our consultations are always free, and there’s never any pressure. Call or text us at 1-855-937-4600 or schedule a call online.

When Should I Sign Up for Medicare? The 3 Enrollment Scenarios