Key Takeaways
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Several Medicare enrollment periods occur annually, and missing them can result in costly late penalties or gaps in coverage.
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In 2025, the addition of new rules and updated enrollment timelines makes it more important than ever to stay ahead of deadlines.
Why Medicare Deadlines Matter More Than You Think
Medicare isn’t just about picking a health plan—it’s about knowing when to act. If you miss certain Medicare deadlines, you may face delayed coverage, permanent late enrollment penalties, or even go without prescription drug protection. In 2025, some deadlines have been adjusted, and others remain fixed, but equally critical.
Understanding the timeline is key. Whether you’re turning 65 this year, retiring later, or reviewing your current plan, marking your calendar for Medicare deadlines is a smart move.
The Initial Enrollment Period (IEP) Is Still the Starting Point
For most people, Medicare eligibility begins at age 65. Your Initial Enrollment Period is your first chance to sign up, and it lasts seven months:
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Starts 3 months before your 65th birthday month
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Includes your birthday month
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Ends 3 months after your birthday month
If you enroll during the first three months, your Medicare coverage starts on the first day of your birthday month. But if you wait until your birthday month or later, your coverage start date may be delayed. That could leave you without coverage for a short period, depending on your situation.
Missing this period entirely? You’ll need to wait for the General Enrollment Period, and that means you could face late penalties.
The General Enrollment Period (GEP) Is Not a Backup Without Consequences
If you didn’t sign up for Medicare when you were first eligible and don’t qualify for a Special Enrollment Period, the General Enrollment Period is your fallback.
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Occurs every year from January 1 to March 31
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Coverage begins July 1 of the same year
This delay in coverage can be risky if you need healthcare services before July. In addition, if you’ve gone more than 12 months without signing up for Part B or Part D, you may incur permanent monthly penalties.
Special Enrollment Periods (SEPs) Cover Specific Circumstances
Not everyone needs to sign up for Medicare at 65. If you’re still working and have employer coverage, you might qualify for a Special Enrollment Period when that coverage ends.
Common scenarios that trigger a Special Enrollment Period include:
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Loss of employer health coverage
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Moving out of your plan’s service area
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Becoming eligible for Medicaid
In these cases, you typically have two months from the date of the event to make changes to your Medicare coverage. In 2025, the rules remain the same, but the Centers for Medicare & Medicaid Services (CMS) is cracking down on misuse, so make sure your reason qualifies.
Medicare Advantage Open Enrollment Is for Current Enrollees Only
If you’re already enrolled in a Medicare Advantage plan, you have an additional window each year to make changes:
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Runs January 1 through March 31
During this time, you can:
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Switch to a different Medicare Advantage plan
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Drop your plan and return to Original Medicare
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Join a standalone Part D plan if you go back to Original Medicare
You can only make one change during this period, so plan carefully. This period is often mistaken for the broader Annual Enrollment Period in the fall, but it is specifically for those who are already enrolled in Medicare Advantage.
Annual Enrollment Period (AEP) Can’t Be Missed
This is the most well-known enrollment period—and for good reason. It’s when anyone with Medicare can:
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Switch between Original Medicare and Medicare Advantage
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Change Medicare Advantage plans
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Join, drop, or change a Part D drug plan
Dates to remember in 2025:
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Starts: October 15
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Ends: December 7
Changes made during this period take effect on January 1, 2026.
If you ignore this window, you’ll be locked into your current coverage until the next year, unless you qualify for a Special Enrollment Period.
The Medicare Prescription Payment Plan Has a New Process in 2025
New in 2025 is the full rollout of the Medicare Prescription Payment Plan, which allows you to spread out your out-of-pocket prescription drug costs over the year rather than paying large amounts all at once.
To opt into this plan, you must:
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Be enrolled in a Medicare Part D plan
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Sign up for the payment plan before the start of each year or within the first month of your plan’s effective date
So if you switch or enroll in a new Part D plan during AEP, you must also opt into the payment plan by the end of January 2026.
Missing this deadline could result in higher upfront drug costs, even if you’re otherwise fully covered.
Late Enrollment Penalties Still Apply in 2025
Penalties are one of the costliest mistakes Medicare enrollees make, and these charges don’t go away. Here’s what to know:
Part B Penalty:
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Applies if you miss your IEP and don’t qualify for a Special Enrollment Period
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Adds 10% for each full 12-month period you were eligible but didn’t enroll
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Stays with you for as long as you have Medicare
Part D Penalty:
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Applies if you go 63 days or more without creditable prescription drug coverage
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Amount depends on how long you were without coverage
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Also lasts as long as you’re enrolled in a Part D plan
Avoiding these penalties means signing up as soon as you’re eligible or when your other coverage ends.
New Deadlines for Those Switching from FEHB to PSHB in 2025
If you’re a retired Postal Service employee, 2025 introduces the new Postal Service Health Benefits (PSHB) program, replacing FEHB coverage. The transition involves specific deadlines:
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You were automatically enrolled in a comparable PSHB plan if you had FEHB coverage in 2024.
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If you wanted to make changes, the enrollment window ran from November to December 2024.
For 2025, unless you experience a qualifying life event, you must wait until the next Open Season to make changes. Don’t assume you can change your plan midyear.
In addition, some PSHB enrollees must be enrolled in Medicare Part B to maintain full coverage. Exceptions apply, but this coordination rule is tied to your eligibility status as of January 1, 2025. Check carefully or risk losing prescription drug coverage.
Deadlines for Changing Medicare Supplement Plans Vary by State
Unlike other parts of Medicare, Medicare Supplement (Medigap) policies don’t follow a uniform national enrollment period after your initial 6-month window following Part B enrollment.
Some states offer limited windows each year to:
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Switch Medigap policies
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Enroll without underwriting
However, many states don’t. In most cases, if you try to change Medigap plans outside your initial window, you may face health screenings, higher costs, or even denial.
Know your state’s rules. While 2025 hasn’t brought major national changes, some state-level adjustments may affect your ability to switch.
Review Your Plan Annually—Don’t Just Auto-Renew
Many people let their plans roll over from one year to the next. While that’s technically allowed, it’s not recommended.
Every year, Medicare plans change:
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Drug formularies update
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Premiums adjust
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Provider networks shift
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Coverage rules evolve
In September, you receive an Annual Notice of Change (ANOC) from your plan. This is your cue to compare your current plan with others during AEP. Ignoring this notice means you may miss out on better coverage—or be surprised by changes in January.
Stay Ahead of the Calendar in 2025
Timing is everything with Medicare. Missing one deadline can set off a chain reaction of costs and complications. In 2025, staying informed means checking your eligibility, understanding new programs, and reviewing your plan annually.
Here’s a quick checklist of critical Medicare deadlines to mark:
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Initial Enrollment Period: Your 7-month window around age 65
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General Enrollment Period: January 1–March 31
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Medicare Advantage Open Enrollment: January 1–March 31
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Annual Enrollment Period: October 15–December 7
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Medicare Prescription Payment Plan: Before plan year or within first month
Planning Your Medicare Timeline Is the Best Way to Protect Your Benefits
Missing a Medicare deadline in 2025 can affect more than just your wallet—it can impact your access to care. Reviewing your options, setting calendar reminders, and reaching out for help when needed can make all the difference.
For a more personalized review of your enrollment options, coverage choices, and timelines, speak with a licensed agent listed on this website who can guide you every step of the way.
