There’s a Deadline to Enroll in Medicare—and It’s Sooner Than You Think

Key Takeaways

• You only have a limited window to sign up for Medicare when you become eligible—miss it, and you could face penalties or coverage gaps.

• Enrollment periods are stricter than many people realize; some deadlines arrive months before your 65th birthday.

Understanding When You’re First Eligible

Turning 65 is a major milestone, especially when it comes to your health coverage. But Medicare doesn’t enroll you automatically unless you’re already receiving Social Security or Railroad Retirement Board benefits. If you’re not, you need to take action yourself.

In 2025, your eligibility begins the month you turn 65. However, your actual enrollment period begins much earlier. This is where many people make a critical mistake.

The 7-Month Initial Enrollment Period (IEP)

Your first opportunity to enroll in Medicare is during your Initial Enrollment Period. It spans seven months:

• Three months before your 65th birthday month

• The month you turn 65

• Three months after your birthday month

Why This Timeline Matters

• If you enroll during the first three months, your coverage starts the month you turn 65.

• If you wait until your birthday month or the three months after, your coverage will be delayed.

• If you miss this window entirely, you may have to wait until the General Enrollment Period (January 1–March 31) the following year, with coverage starting July 1—and possibly late penalties.

General Enrollment Period (GEP) Is Not Ideal

The General Enrollment Period should be your fallback—not your first choice. It runs from January 1 to March 31 each year. If you enroll during this time, your coverage will begin July 1 of the same year.

That means you could be without Medicare for several months if you miss your Initial Enrollment Period.

In addition, you may owe late enrollment penalties, which are added to your premiums:

• For Part B: A 10% increase for every 12-month period you were eligible but didn’t enroll.

• For Part A: Penalties apply only if you don’t qualify for premium-free Part A.

Special Enrollment Periods (SEP) Can Help—but Only Sometimes

If you’re still working or have credible employer coverage when you turn 65, you may be eligible for a Special Enrollment Period once that coverage ends.

This SEP:

• Lasts for 8 months from the time your job-based insurance ends

• Lets you avoid late penalties

But don’t assume you’re eligible—this only applies if your coverage was active when you became eligible for Medicare.

Employer Coverage Doesn’t Always Delay the Deadline

Many assume they can delay enrolling in Medicare if they have any kind of coverage. But this only works if it’s creditable coverage, typically defined as:

• Employer group health plans from a company with 20 or more employees

• COBRA does not count as creditable coverage for delaying Part B

• Retiree insurance also does not qualify

If you’re unsure about your employer plan’s status, ask your HR department or benefits administrator. You must get this right to avoid penalties later.

Automatic Enrollment Scenarios

You are automatically enrolled in both Medicare Part A and Part B if:

• You’re receiving Social Security or Railroad Retirement benefits at least four months before turning 65

• You live in the U.S. (automatic enrollment doesn’t apply if you live abroad)

You’ll receive your Medicare card in the mail about three months before your 65th birthday. If you want to decline Part B (to avoid premiums, for example), you’ll need to follow the instructions in the letter that accompanies your card.

Delaying Part B—But Not Part A

Most people don’t pay a premium for Part A, so they usually enroll as soon as they’re eligible. But some choose to delay Part B to avoid the monthly premium if they still have other coverage.

Before doing this, make sure:

• Your current coverage is creditable

• You’re aware of the 8-month SEP for Part B

• You understand that waiting longer may cause a permanent late penalty

Remember: The SEP doesn’t extend beyond the 8 months, even if you have COBRA or retiree coverage afterward.

Medicare Advantage and Part D Have Their Own Enrollment Deadlines

If you want to enroll in Medicare Advantage (Part C) or Prescription Drug Coverage (Part D), those options follow different rules:

• You must first enroll in Parts A and B

• You can sign up for a Part D plan or Medicare Advantage plan during your IEP

• If you miss your IEP, you may have to wait until the Annual Enrollment Period (October 15–December 7)

If you delay Part D and don’t have creditable drug coverage in the meantime, you’ll owe a late enrollment penalty that lasts as long as you have coverage.

Avoiding Penalties Requires Advance Planning

The single most common mistake people make is assuming Medicare will notify them or enroll them automatically. Unless you’re already on Social Security benefits, it’s up to you to enroll.

Here’s what to do:

• Mark your calendar for three months before your 65th birthday

• Visit the official Medicare website or call Social Security to begin the process

• Make sure you understand whether your current insurance counts as creditable coverage

Procrastination can lead to permanent penalties and months of uncovered medical costs.

What Happens If You Retire After 65?

If you retire after age 65 and had creditable employer coverage while working, you can use the Special Enrollment Period to sign up for Medicare without penalties.

However:

• You must apply within 8 months of losing job-based coverage

• Your Part B coverage will begin the month after you enroll

Don’t confuse the end of employment with the end of coverage. Your SEP window starts the moment your coverage ends, not your job.

Do You Need to Sign Up for Part A Separately?

In most cases, Part A enrollment is straightforward:

• If you’re not enrolled automatically, you can sign up during your IEP

• You won’t be penalized for delaying it if you’re not eligible for premium-free Part A

However, people who aren’t eligible for free Part A and choose not to enroll when first eligible may face a 10% premium penalty for twice the number of years they delayed.

If You’re Under 65 With a Disability

You become eligible for Medicare after 24 months of receiving Social Security Disability Insurance (SSDI). In that case:

• You’re usually enrolled automatically after your 24th month of benefits

• Your Medicare card should arrive about three months before coverage starts

No action is needed unless you want to delay coverage, which could still result in penalties.

What to Do Right Now

Timing is everything. Here’s what you should check today:

• Are you within three months of turning 65?

• Are you already receiving Social Security benefits?

• Do you have employer insurance that qualifies as creditable coverage?

• Have you reviewed your options for drug coverage or Medicare Advantage?

The earlier you act, the better your chances of avoiding delays or extra costs.

Medicare Enrollment Deadlines Are Easy to Miss—But You Don’t Have To

The Medicare system isn’t built around reminders or forgiveness. The burden is on you to know when to enroll, confirm your eligibility, and check whether your current coverage meets the criteria.

Missing a deadline can lead to coverage gaps or permanent financial penalties. To avoid that, speak with a licensed agent listed on this website who can help you review your options, confirm eligibility, and walk you through the correct timeline for enrollment.