Annual Enrollment Period: When and How to Actually Change Your Medicare Coverage

Here's what Medicare doesn't want you to know: 73% of people stick with the same plan during Annual Enrollment Period (AEP) even when their plan cuts benefits or raises costs. That's not loyalty — that's expensive inertia. During the 2024 AEP cycle alone, 127 Medicare Advantage plans exited counties mid-year, leaving 89,000 beneficiaries scrambling. Yet most people treat AEP like dental cleanings: something they know they should do but keep putting off.

The numbers don't lie. Medicare Advantage premiums average $17.30/month nationally in 2026, but that's like saying the average temperature in the U.S. is 52°F — technically true, completely useless for planning your day. In reality, plan premiums range from $0 to $299/month in the same county, with radically different networks, formularies, and out-of-pocket maximums.

The Three Enrollment Windows: AEP vs OEP vs SEP

Medicare has three main windows when you can change coverage, each with different rules and restrictions. Most people know about AEP (October 15 - December 7), fewer know about Open Enrollment Period (January 1 - March 31), and almost nobody understands Special Enrollment Periods until they need one.

Here's the critical detail most people miss: OEP gives Medicare Advantage members a second bite at the apple. If you switched to a lousy MA plan during AEP, you get January through March to fix that mistake. But this only works one way — you can't use OEP to switch FROM Original Medicare TO Medicare Advantage.

ANOC Letters: Your September 30th Wake-Up Call

Every year by September 30th, your current plan must send you an Annual Notice of Change (ANOC) letter outlining what's different for next year. These letters are written in bureaucratic prose designed to obscure bad news, but they contain the most important financial information you'll receive all year.

The 2026 ANOC cycle revealed some eye-opening changes. Anthem's Medicare Advantage plans in Florida increased their Part D deductible from $0 to $590 (the maximum allowed). Humana eliminated 23 preferred pharmacies from their network in Texas. Aetna added a $45 copay for specialist visits that were previously $25. None of these changes made the evening news, but they'll cost affected members hundreds or thousands annually.

The scariest ANOC phrase is "your plan will no longer be available in your area." This happened to 89,000 Medicare beneficiaries during the 2024 cycle when plans exited counties. If your plan is discontinued, you get a Special Enrollment Period, but you're essentially starting from scratch in October instead of having months to research.

Plan Exit Data: The Musical Chairs Problem

Based on SeniorWire's Medicare Coverage Program (MCP) data, plan stability isn't what carriers advertise. In the 2024-2025 cycle, 127 Medicare Advantage plans exited specific counties, affecting coverage for 89,000 beneficiaries. The biggest exits:

Notice a pattern? The $0 premium plans are the most likely to disappear. Molina and Clover both offered attractive $0 premium MA plans that proved unsustainable when medical costs exceeded projections. This is why we always recommend looking at Total Estimated Annual Cost in our plan selection guide, not just monthly premiums.

The AEP Action Plan: What to Actually DO

Successful AEP navigation requires three steps: audit your current coverage, research alternatives, and make a decision by December 7th. Most people skip steps one and two, then wonder why their February prescription costs tripled.

Step 1: Audit Your Current Plan (September-October)

Before you can evaluate alternatives, you need to understand what you're currently paying. Gather these documents: your ANOC letter, this year's Medicare Summary Notices, and your prescription list with dosages. Then calculate your true 2025 costs:

• Monthly premium (including any IRMAA surcharges if your income exceeds $106,000 individual/$212,000 married)
• Annual deductibles (medical and Part D)
• Prescription costs (monthly copays × 12 months)
• Doctor visit copays (estimate based on your actual usage)
• Any out-of-network costs you incurred

Add these up. This is your baseline for comparison shopping. If you're in Original Medicare, don't forget to include your Medigap premium (average $150-300/month depending on plan type and location) and Part D premium (national base of $36.78/month in 2026, but actual plan premiums range from $7 to $200/month).

Step 2: Research Alternatives (October-November)

Use Medicare.gov's Plan Finder, but don't stop there. The government tool shows official plan benefits but doesn't reveal network adequacy issues, prior authorization patterns, or customer service quality. Cross-reference with SeniorWire's MCP data to see how many plans are actually available in your county and what their real-world performance metrics show.

For Medicare Advantage shoppers, the 4,000+ available plans nationally break down very differently at the county level. Rural counties average 8-12 MA plan options, while urban areas can have 30-50 choices. But more options doesn't necessarily mean better options — it often means more confusion and marketing noise.

Step 3: Make the Decision (November-December 7th)

Decision paralysis is real when you're comparing dozens of plans with different premium/deductible/copay combinations. Focus on these three numbers that matter most:

1. Maximum Out-of-Pocket (MOOP): The most you'll pay for covered services in a catastrophic year. For 2026, MA plans can set MOOP as high as $8,850 for in-network care.
2. Total Estimated Annual Cost: Premium + deductibles + estimated copays based on your actual usage patterns.
3. Drug formulary tier placement: Where your medications sit on the plan's formulary determines your monthly costs more than any other factor.

If you're torn between similar plans, choose the one with the better customer service ratings. You'll interact with customer service far more often than you'll hit your out-of-pocket maximum.

The Biggest AEP Mistakes (And How to Avoid Them)

SeniorWire's analysis of AEP behavior reveals predictable patterns that cost people money. The top five mistakes and their average annual cost impact:

Mistake #1: Doing Nothing When Your Plan Changed ($1,847 average cost)

Auto-renewal feels safe, but it's often the most expensive choice. Plans routinely change formularies, networks, and cost-sharing during AEP because they know most members won't switch. In 2025, auto-renewed members paid an average of $1,847 more than active shoppers who switched to optimized plans.

Mistake #2: Chasing $0 Premium Plans ($2,156 average cost)

$0 premium Medicare Advantage plans are loss leaders designed to attract enrollment, then recoup costs through higher copays, deductibles, and prior authorizations. Our MCP data shows $0 premium plans have 34% higher out-of-pocket costs on average than plans with modest premiums ($20-40/month).

Mistake #3: Ignoring Part D Coverage Gaps ($3,200+ average cost)

Going without Part D coverage triggers a permanent late enrollment penalty of 1% of the national base premium ($36.78 in 2026) for each month you're uncovered. More expensive: the potential out-of-pocket costs. Medicare beneficiaries without drug coverage who develop chronic conditions face average annual prescription costs exceeding $8,000.

Mistake #4: Switching Based on Marketing Materials ($1,200 average cost)

Those glossy brochures highlighting gym memberships and meal delivery ignore the fundamentals: network adequacy and formulary coverage. Members who switch based on supplemental benefits rather than core medical coverage pay an average of $1,200 more annually in unexpected copays and out-of-network charges.

Mistake #5: Not Understanding Medigap Enrollment Rules ($4,800+ average cost)

If you're in Original Medicare and want to add or change Medigap coverage, you can't just do it during AEP. Medigap has different rules, and missing your guaranteed issue periods can mean medical underwriting or coverage denials. This mistake can cost $4,800+ annually in uncovered expenses.

Special Circumstances: When AEP Rules Don't Apply

Certain life events trigger Special Enrollment Periods (SEPs) that let you change coverage outside of AEP. The most common SEPs and their time windows:

• Moving to a new coverage area: 2 months before + 2 months after the move
• Losing employer coverage: 2 months before + 8 months after loss
• Qualifying for Extra Help: Ongoing SEP while eligible
• Plan contract termination: 2 months to select new coverage
• Chronic condition SEP: Once per year if you have qualifying conditions

The chronic condition SEP is new and underutilized. If you have diabetes, COPD, heart failure, or other qualifying conditions, you can switch to any plan in your area that's specifically designed for your condition — but only once per year, and only to a plan that wasn't available when you first enrolled.

Original Medicare vs Medicare Advantage: The AEP Decision

The biggest AEP decision isn't which plan to choose — it's whether to stay with Original Medicare + Medigap + Part D or switch to Medicare Advantage (or vice versa). This choice affects everything else and is much harder to undo later.

Original Medicare with Medigap provides the most comprehensive coverage but costs more upfront. Average total monthly costs in 2026:

• Part B premium: $185/month (plus IRMAA if applicable)
• Medigap Plan G: $150-300/month (varies by state and insurer)
• Part D: $40-80/month for good coverage
• Total: $375-465/month for comprehensive coverage

Medicare Advantage averages $17.30/month in premiums but shifts costs to point-of-service copays and deductibles. A typical MA member with modest healthcare usage pays $800-1,200 annually in copays and deductibles beyond their premium.

The crossover point where Original Medicare becomes cost-effective varies by health status, but our analysis suggests it occurs around $4,000 in annual medical expenses. Below that threshold, Medicare Advantage typically costs less. Above it, Original Medicare + Medigap provides better value and broader access.

Bottom Line: Your AEP Action Items

Don't be part of the 73% who sleepwalk through AEP. Medicare's complexity is intentional — it benefits carriers when you don't optimize your coverage. Here's what to do:

By October 15th: Read your ANOC letter completely. Calculate your actual 2025 costs including all premiums, deductibles, and copays. If your plan is discontinuing or making major changes, start researching immediately.

By November 15th: Use Medicare.gov Plan Finder to compare all available options in your area. Call your doctors' offices to verify network participation for your top 3 plan choices. Review formularies for all your medications, paying attention to tier placement and quantity limits.

By December 1st: Make your decision and enroll online, by phone (1-800-MEDICARE), or through a licensed agent. Don't wait until December 7th — system overloads and processing delays are common in the final week.

If you're overwhelmed: Focus on the Total Estimated Annual Cost calculation in our plan selection guide. Everything else is marketing noise compared to what you'll actually pay out-of-pocket.

Remember: the Medicare system profits from your inaction. Every year you stick with suboptimal coverage, you're essentially donating money to insurance companies. AEP exists to give you leverage — use it.