What Happens If You Miss Medicare's Annual Enrollment Period?

Missed Medicare's Annual Enrollment Period? Here's what your options actually are, what it costs you, and how to avoid being stuck without coverage.

Author: Lynsey Brennan, Licensed Medicare Advisor | Published October 10, 2026 Reading time: 6 min read

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Quick Answer

Medicare's Annual Enrollment Period (AEP) runs October 15 through December 7 each year. If you miss it, you generally cannot switch or add Medicare Advantage or Part D drug coverage until the next AEP — unless you qualify for a Special Enrollment Period. Missing the deadline can mean staying in a plan that no longer fits your needs, and in some cases, paying late-enrollment penalties.

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Key Takeaways

• AEP closes December 7 every year — changes take effect January 1 of the following year.
• Missing AEP does not cancel your existing Medicare coverage; you stay in whatever plan you have.
• Some life events — moving, losing employer coverage, gaining Medicaid — may qualify you for a Special Enrollment Period.
• A Part D late-enrollment penalty can follow you for life if you go without creditable drug coverage.
• Arizona Medicare enrollees have more plan options than many states, but those options still close with AEP. Check 2026 Medicare costs before assuming your current plan is still the best fit.

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Table of Contents

1. What AEP Actually Is — and What It Covers 2. What Happens to Your Current Coverage 3. Special Enrollment Periods: Your Backup Option 4. The Part D Late-Enrollment Penalty — A Real Financial Risk 5. Arizona-Specific Considerations 6. Medicare Advantage vs. Supplement: Which One You're Stuck With Matters 7. How to Make Sure This Doesn't Happen Again

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What AEP Actually Is — and What It Covers {#what-aep-actually-is}

The Annual Enrollment Period is the one window each year when any Medicare beneficiary — regardless of health status — can make changes to their Medicare Advantage or Part D drug plan. It runs October 15 through December 7, with changes taking effect January 1.

During AEP, you can:

• Switch from one Medicare Advantage plan to another
• Switch from Medicare Advantage back to Original Medicare (Parts A and B)
• Add, drop, or change a standalone Part D drug plan
• Switch from Original Medicare to a Medicare Advantage plan

What AEP does not cover: enrolling in Medicare for the first time (that's your Initial Enrollment Period) or making changes to a Medicare Supplement (Medigap) policy in most states.

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What Happens to Your Current Coverage {#what-happens-to-your-current-coverage}

Missing AEP does not mean you lose Medicare. You stay enrolled in whatever plan you currently have — whether that's Original Medicare, a Medicare Advantage plan, or a Part D drug plan.

The problem is that plans change every year. Premiums, formularies (the list of covered drugs), provider networks, and cost-sharing can all shift on January 1. If you miss AEP, you're locked into whatever your current plan has become, even if the changes aren't in your favor.

That's worth taking seriously. The 2026 standard Part B premium is $202.90/month, and the Part B deductible is $283 (CMS, November 2025). Those are baseline costs on top of any plan premiums — and they don't budge just because your plan's benefits changed in a direction you didn't expect.

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Special Enrollment Periods: Your Backup Option {#special-enrollment-periods}

Missing AEP isn't always the end of the road. Certain life events trigger a Special Enrollment Period (SEP) that lets you make changes outside of AEP. Common qualifying events include:

• Moving to a new service area where your current plan isn't available
• Losing other creditable coverage, such as employer or union insurance
• Gaining or losing Medicaid eligibility
• Moving into or out of a skilled nursing facility or long-term care facility
• Your plan leaving the Medicare program or losing its contract

SEPs are time-limited — typically you have two months from the qualifying event to act. If you think you may qualify for one, don't wait. Visit our Medicare enrollment periods guide for a full breakdown.

There's also the Medicare Advantage Open Enrollment Period (OEP), which runs January 1 through March 31. During OEP, if you're already enrolled in a Medicare Advantage plan, you can switch to a different Medicare Advantage plan or return to Original Medicare (and add a Part D plan). This is not a full do-over of AEP — it's more limited — but it's something.

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The Part D Late-Enrollment Penalty — A Real Financial Risk {#the-part-d-penalty}

If you don't have Part D drug coverage and you didn't have other creditable drug coverage when you first became eligible, the late-enrollment penalty can stack up fast. The penalty is roughly 1% of the national base beneficiary premium for every month you went without coverage — and it's added to your Part D premium permanently.

The 2026 annual out-of-pocket threshold for covered Part D drugs is $2,100 (CMS CY 2026 Part D benefit parameters). Covered insulin is capped at $35/month under Medicare Part D. These protections only apply if you're actually enrolled in Part D — which is another reason letting coverage lapse carries real risk.

If you're unsure whether your current coverage qualifies as creditable, our Part D drug coverage guide explains what counts and what doesn't.

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Arizona-Specific Considerations {#arizona-specific-considerations}

Arizona Medicare beneficiaries typically have a solid range of Medicare Advantage plan options, particularly in the Phoenix and Tucson metro areas. Plans from carriers like UnitedHealthcare, Humana, Aetna, and Blue Cross Blue Shield of Arizona have historically competed for enrollees in these markets.

That competition can work in your favor — but only if you're making active choices. Missing AEP means missing your chance to compare updated plan formularies, updated provider networks, and any new $0-premium options that may have entered the Arizona market for 2026.

If you've moved to Arizona from another state — a common situation for retirees — check whether your current plan even covers your new zip code. A move is often a qualifying SEP event, which could give you a window to make changes even after AEP closes.

For a broader look at how Arizona compares nationally: national Medicare Advantage enrollment is now about 54% of all Medicare beneficiaries (CMS, 2024). Arizona's numbers track closely with that trend, making Medicare Advantage plan selection especially important for Arizona Medicare enrollees.

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Medicare Advantage vs. Supplement: Which One You're Stuck With Matters {#advantage-vs-supplement}

The stakes of missing AEP differ depending on what type of coverage you have. With Medicare Advantage, you're locked into a network-based plan with annual benefit changes. Missing AEP means staying in that plan's updated structure — for better or worse.

With Original Medicare plus a Medicare Supplement (Medigap), AEP doesn't affect your Medigap policy at all. Medigap plans don't change during AEP. However, if you want to add or change a Part D drug plan, AEP still applies.

The 2026 Medicare Advantage out-of-pocket maximum cap for in-network services is $9,250 (CMS, Final CY 2026 Part C bid-review memorandum, Table 3). Whether that cap is adequate for your health situation is worth reviewing annually. Our Medicare Advantage vs. Supplement comparison can help you think through the trade-offs honestly — there's no one-size-fits-all answer.

You can also use our plan comparison tool to look at options side by side.

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How to Make Sure This Doesn't Happen Again {#how-to-prevent-this}

Mark October 15 on your calendar now — every year. When your Annual Notice of Change (ANOC) arrives in late September, read it. That document tells you exactly what's changing in your plan for the coming year.

A few practical habits help:

• Review your drug list annually. Formularies change. A medication that was Tier 2 may move to Tier 4.
• Verify your doctors are still in-network, especially if you have a Medicare Advantage HMO.
• Don't assume last year's plan is still the best option. New plans enter markets, and existing plans adjust benefits.

A licensed Medicare advisor can do this review with you at no cost. It takes about 30 minutes and can flag issues you'd otherwise miss.

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Frequently Asked Questions

Q: If I miss AEP, can I still switch Medicare plans? A: In most cases, no — not until the next AEP, which opens October 15. However, if you qualify for a Special Enrollment Period due to a life event like moving or losing other coverage, you may be able to make changes outside of AEP. The Medicare Advantage Open Enrollment Period (January 1-March 31) also allows limited plan changes if you're already in a Medicare Advantage plan.

Q: Does missing AEP mean I'll lose my Medicare coverage? A: No. Missing AEP does not cancel your coverage. You remain enrolled in your current plan, which typically auto-renews for the next calendar year — even if that plan's benefits, premiums, or drug formulary have changed.

Q: What is the Part D late-enrollment penalty and how is it calculated? A: The penalty is approximately 1% of the national base beneficiary premium multiplied by the number of months you went without creditable drug coverage. It's added to your monthly Part D premium and typically applies for as long as you have Part D — so the longer the gap, the higher the ongoing cost.

Q: Are Arizona Medicare plan options different from other states? A: Arizona, particularly in Phoenix and Tucson, tends to have a competitive Medicare Advantage market with multiple carriers offering plans each year. That said, plan availability, premiums, and networks vary by zip code, and options in rural Arizona can be more limited. Reviewing your specific area annually is the only reliable way to know what's available to you.

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The Bottom Line

Missing Medicare's Annual Enrollment Period usually means staying put in your current plan for another full year — even if that plan's benefits, costs, or network have shifted in ways that don't work for you. It's not a disaster, but it can be an expensive inconvenience. If you think a Special Enrollment Period might apply to your situation, or you simply want to make sure you're in the right plan before December 7 closes the window, let's talk.

Schedule your free Medicare review today — no pressure, no obligation, just a straight conversation about what makes sense for your situation.

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Sources

• CMS Medicare Monthly Enrollment, 2024 — national and state Medicare Advantage enrollment figures
• CMS, November 2025 — 2026 Part B premium ($202.90/month) and Part B deductible ($283)
• CMS CY 2026 Part D Benefit Parameters — 2026 annual out-of-pocket threshold ($2,100) and insulin cap ($35/month)
• CMS, Final CY 2026 Part C Bid Review Memorandum (April 16, 2025), Table 3 — 2026 maximum in-network out-of-pocket limit for HMO and PPO plans ($9,250)
• CMS Medicare General Information — Annual Enrollment Period dates and rules
• Medicare.gov — Special Enrollment Period qualifying events
• Medicare.gov — Part D late-enrollment penalty calculation methodology

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This article is for educational purposes and is not affiliated with or endorsed by the federal Medicare program or any government agency. HealthPlan Connect is a private, licensed Medicare advisory service. FL License #G007269.