A short summary up top before diving in: Medicare has several distinct enrollment windows, and missing the wrong one can cost you more every single month for life. This guide breaks down every period you need to know, explains the late-enrollment penalty in plain numbers, and covers a Nevada-specific rule that most people in Las Vegas never hear about until it’s too late.
The Window You Can’t Afford to Miss: Your Initial Enrollment Period
When you turn 65, Medicare gives you a seven-month window to sign up for Parts A and B. That window opens three months before your birthday month, includes your birthday month itself, and closes three months after. So if your birthday is August 15, your Initial Enrollment Period (IEP) runs from May 1 through November 30.
If you’re already collecting Social Security, you’ll be enrolled in Original Medicare automatically your card shows up in the mail about three months before your coverage starts. But if you haven’t claimed Social Security yet, you need to sign up yourself through SSA.gov or your local Social Security office.
One timing nuance worth knowing: if you enroll during the three months after your birthday month, your coverage doesn’t start until the first of the following month. Enrolling during or before your birthday month gets you the earliest possible start date. Small detail, but it matters if you’re timing a retirement.
What Happens If You Miss It
This is where things get expensive.
If you don’t sign up for Part B during your IEP and you don’t have a qualifying reason to delay, you’ll pay a late enrollment penalty 10% added to your monthly Part B premium for every full 12-month period you went without coverage. And it isn’t a one-time fee. You carry it for as long as you have Medicare.
The standard Part B premium in 2026 is $202.90 per month. Miss your window by two full years and your premium jumps by 20%, bringing your monthly cost to roughly $243. Miss it by five years and you’re looking at a 50% surcharge permanently.
That’s real money, year after year.
Part D (prescription drug coverage) works the same way: 1% of the national base beneficiary premium added per month you went uncovered, tacked on permanently once you do enroll.
Still Working at 65? Here’s Your Exception
If you’re 65 or older and still covered by a current employer’s group health plan either your own job or your spouse’s you can delay Medicare without penalty. The operative word is current. COBRA doesn’t count. Retiree coverage doesn’t count. Only active, employer-sponsored coverage qualifies.
When that employer coverage ends, you get an eight-month Special Enrollment Period (SEP) to sign up for Parts A and B without penalty. However, for Part C (Medicare Advantage) and Part D, the window is just the first two months of that eight-month stretch. A lot of people miss that distinction and end up scrambling.
One more trap: some people retire, take COBRA to bridge their coverage, and assume the COBRA window extends their Medicare enrollment period. It does not. The eight-month clock starts when your active employment or employer coverage ends not when your COBRA runs out. Enroll based on your job end date, even if you’re using COBRA for other reasons.
The Annual Enrollment Period (and When It Actually Applies to You)
Every fall, from October 15 through December 7, Medicare runs its Annual Enrollment Period (AEP). You’ve seen the TV commercials. Here’s what it actually covers: if you already have Medicare Parts A and B, you can use AEP to switch Medicare Advantage plans, switch Part D drug plans, or move between Medicare Advantage and Original Medicare.
If you’re brand new to Medicare, AEP does not replace your Initial Enrollment Period. It’s for people who already have coverage and want to change it.
There’s also a Medicare Advantage Open Enrollment Period from January 1 through March 31. During this window, if you’re already in a Medicare Advantage plan, you can switch to a different Advantage plan or go back to Original Medicare. You cannot, however, use this period to pick up a Medigap policy with guaranteed issue rights that’s a separate process.
A Las Vegas-Specific Rule Most People Don’t Know About
Nevada passed Assembly Bill 250, which created a Birthday Rule for Medicare Supplement (Medigap) policyholders. Effective January 1, 2022, if you already have a Medigap plan in Nevada, you get a 60-day window beginning the first day of your birthday month each year during which you can switch to a Medigap plan of equal or lesser benefits no medical underwriting required.
That means insurance companies cannot ask about your health history, cannot charge you more because of a pre-existing condition, and cannot deny you during that window.
Why does this matter? Medigap premiums tend to increase over time. Outside of your original open enrollment period, switching Medigap plans normally requires you to pass medical underwriting, which can mean higher rates or an outright denial if your health has changed. Nevada’s Birthday Rule gives you one guaranteed shot each year to shop for a lower premium without that risk.
Note that this applies only to current Medigap policyholders. If you’re on Medicare Advantage, the Birthday Rule doesn’t apply to you.
The General Enrollment Period: Your Last Resort
If you missed your IEP and don’t qualify for a Special Enrollment Period, you can sign up for Parts A and B during the General Enrollment Period January 1 through March 31 each year, with coverage starting the first of the following month. You will, however, likely owe the late enrollment penalty going forward. It’s not an ideal situation, but it’s the path forward if you find yourself in it.
FAQ
When exactly does my Medicare Initial Enrollment Period start?
Your IEP is a seven-month window: it opens three months before the month you turn 65, includes your birthday month, and closes three months after. It’s tied to your specific birth month, not any calendar-year window.
Can I delay Medicare if I’m still working at 65?
Yes, if you’re covered by an active employer’s group health plan (your own or your spouse’s), you can delay without penalty. When that coverage ends, you get an eight-month Special Enrollment Period for Parts A and B. COBRA and retiree coverage do not qualify for this exception.
What is the Part B late enrollment penalty?
For each full 12-month period you went without Part B coverage (and without a qualifying exception), 10% is permanently added to your monthly premium. With the 2026 standard premium at $202.90, two years without coverage adds roughly $40 a month for life.
What is Nevada’s Birthday Rule for Medicare Supplement?
Nevada’s AB 250 Birthday Rule gives existing Medigap policyholders a 60-day window starting on the first day of their birthday month each year to switch to a Medicare Supplement plan of equal or lesser benefits no medical underwriting, no health questions. It’s a Nevada-specific protection that can help you lower premiums as you age.
Does the Annual Enrollment Period in the fall apply to me if I’m new to Medicare?
Not for your initial enrollment. The Annual Enrollment Period (October 15–December 7) is for people who already have Medicare coverage and want to change plans. If you’re turning 65, focus on your Initial Enrollment Period first.
What if I missed my enrollment window entirely?
If you don’t qualify for a Special Enrollment Period, you’ll need to wait for the General Enrollment Period (January 1–March 31) and will likely face a late enrollment penalty. A local Medicare advisor can review your situation and help determine whether any exceptions apply.
Medicare enrollment isn’t complicated once you know which window applies to your situation but the windows are narrow, the penalties are permanent, and the rules have enough exceptions and state-specific wrinkles (looking at you, Nevada Birthday Rule) that it’s easy to make a costly mistake on your own.
If you’re turning 65, retiring, or just trying to figure out whether your current plan is still the right fit, contact Aidan Neshite at The Perl Path today for a free consultation. Reach him directly at 702-503-8344 no pressure, no cost, just clear answers.
