Your Medicare Initial Enrollment Period is a 7-month window built around your 65th birthday, and it’s the only chance most people get to sign up for Part A and Part B without a penalty attached. It runs from 3 months before your birth month through 3 months after it. If You miss the enrollment window you can end up with a penalty that follows you for as long as you have Medicare. Here’s how the 7 months break down, when coverage actually starts, and what to check before you sign anything.
What Is the Medicare Initial Enrollment Period?
The Initial Enrollment Period (IEP) is the 7-month window when you first become eligible to sign up for Medicare Part A and Part B. For most people that’s the period surrounding their 65th birthday, though people who qualify for Medicare earlier due to disability have their own IEP tied to their 24th month of disability benefits. Once Part A and Part B are in place, most people also shop for a Medicare Supplement (Medigap) policy to help cover the deductibles, copays, and coinsurance that Original Medicare leaves behind. Click here if you are New to Medicare and not sure where to start. .
When Does Your 7-Month Window Start?
Count 3 months back from your birth month, and that’s the first month of your IEP. Your window then includes your birth month itself and extends 3 months past it, for 7 months total. If your birthday falls on the first of the month, Medicare says you can start 1 month before you turn 65 so factor that shift in when you apply. Source: Medicare.gov.
💡 Tip: Set a reminder for 3 months before your birthday, not the birthday itself. Signing up early in your window is what gets you coverage the month you actually turn 65, instead of a month or two later.
When Will Your Medicare Coverage Actually Start?
Coverage always starts on the first of a month, but which month depends on when in your 7-month window you sign up. As of 2026, the rule is simpler than it used to be: sign up any time before the month you turn 65 and coverage starts the month you turn 65. Sign up during your birth month or any of the 3 months after, and coverage starts the very next month, with no waiting period attached. That’s a change from the rules before 2023, when signing up late in the window could delay coverage by up to 3 months.
| If You Sign Up: | Coverage Starts: |
|---|---|
| Any of the 3 months before your birth month | The month you turn 65 |
| Your birth month, or any of the 3 months after | The first day of the next month |
Source: Medicare.gov.
What Happens If You Miss Your Initial Enrollment Period?
If your 7 months pass and you haven’t signed up, your next chance is the General Enrollment Period, which runs January 1 through March 31 every year, with coverage starting the month after you sign up. Waiting usually comes with a cost. The Part B penalty adds 10% to your premium (currently $202.90 per month) for every full 12-month period you went without Part B or other coverage that counts as similar, and it’s generally charged for as long as you have Part B. If you have to pay for Part A because you don’t qualify for the premium-free version, that penalty works differently: you pay the extra 10% for twice the number of years you delayed. Source: Medicare.gov.
None of the penalties apply if you qualify for a Special Enrollment Period, most commonly because you or your spouse are still covered by a current employer’s group health plan when your IEP ends. See below
Still Working at 65? Here’s How the Window Changes
If you or your spouse are actively working and covered by an employer plan with 20 or more employees, you can typically delay Part B past your IEP without a penalty, then sign up during an 8-month Special Enrollment Period that starts the month employment or the group coverage ends (whichever comes first). COBRA and retiree coverage don’t count as active employer coverage for this purpose, so they don’t extend your window. Many people still take Part A during their IEP even while working, since it’s usually premium-free.
📌 Note: If you’re contributing to a Health Savings Account (HSA), Part A enrollment can be backdated up to 6 months and may trigger a tax penalty on recent HSA contributions. That’s a tax question, not something our team advises on, so check with your HR department or tax advisor before you enroll if you’re still contributing to an HSA.
How Medigap Fits Into Your Initial Enrollment Period
Once your Part B coverage takes effect, a separate 6-month Medigap Open Enrollment Period begins. During those 6 months, you can buy any Medigap policy sold in your state at the best available price, with no medical underwriting and no denials for pre-existing conditions. Some people call this window Medsupp initial open enrollment open enrollment; it’s the same 6-month period regardless of what you call the product. If you miss it, buying a Medigap plan later generally means going through medical underwriting instead.
Remember: You can apply for Medigap at any time of year using underwriting and approval is possible even with some pre-existing conditions.. Our Medigap Underwriting Checker will explain how it works and you can check any health issues there.. A handful of states also offer guaranteed-issue windows without underwriting.
Get a Medigap Quote Enroll in Medigap
If you’re weighing Medigap against Medicare Advantage during your IEP, it’s worth comparing both before you commit, since switching later isn’t always simple. Our Medigap vs. Medicare Advantage comparison and Medigap overview cover the tradeoffs in more detail.
What to Do Before Your Window Closes
Mark the 3-month point before your birthday on your calendar, confirm whether an employer plan lets you delay Part B, and decide early whether you’re leaning toward Medigap or Medicare Advantage so your 6-month Medigap Open Enrollment Period doesn’t slip by unused. If you’re ready to compare Medigap plans and pricing for your state, get a quote at Senior65.com or call 800-930-7956 to speak with our team. Our help is free, and by law no one can offer you a lower price on the same plan.