What Is the Medicare Annual Notice of Change (ANOC)

The Medicare Annual Notice of Change — universally referenced in the industry by its initialism ANOC — is one of the most consequential pieces of mail a Medicare beneficiary receives all year, and one of the most consistently underread. If you are enrolled in a Medicare Advantage plan or a Medicare Part D prescription drug plan, your insurance carrier is legally required to send you an ANOC every fall, and that document contains information that can directly affect how much you pay for healthcare in the coming year, which doctors and facilities you can access, what you pay for your prescriptions, and what supplemental benefits remain available to you. The document is not marketing material. It does not require a response. But ignoring it while assuming that nothing important has changed can lead to financially painful surprises in January when new plan terms take effect and you discover that your primary care physician left the network, a maintenance medication moved to a higher cost tier, or your maximum out-of-pocket exposure increased by thousands of dollars — none of which your current plan was required to warn you about in any format other than the ANOC you received the previous September.

Medicare Advantage and Part D plans operate on calendar-year contracts that are refiled with the Centers for Medicare & Medicaid Services (CMS) annually. Every year, carriers have the opportunity — and the obligation — to revise their benefit structures, cost-sharing arrangements, provider networks, formulary designs, and premium levels for the coming year. These changes can be modest in some years and substantial in others, and there is no requirement that the changes be favorable to beneficiaries. A plan that served a beneficiary’s needs well in the current year may be structured very differently in the coming year, and the ANOC is the mechanism through which the beneficiary receives that year-to-year comparison in writing before the Annual Election Period — the window from October 15 through December 7 during which plan changes can be made for the following year. Understanding your ANOC, reading it carefully, and acting on its content during the AEP window is how you ensure that your Medicare coverage continues to serve your actual healthcare needs rather than automatically defaulting to whatever terms your carrier has set for the coming year.

This page covers the Medicare ANOC in comprehensive practical detail: what it is and what it is not, who receives it, when it arrives and why the timing matters, what each of its key sections communicates and what to look for in each, how it connects to the Annual Election Period and the planning decisions that window requires, how it differs from the Evidence of Coverage, and how Medicare coverage decisions fit within a broader retirement healthcare and financial planning framework. For the foundational context on how Medicare plan types compare structurally, our resource on Medicare Advantage vs. Medicare Supplement comparison covers the essential distinction between plan types that determines which documents apply to you — including why ANOC recipients are a different population than Medicare Supplement enrollees. Our broader Medicare services overview covers the full scope of Medicare planning support we provide, and our best independent Medicare broker resource covers how independent broker representation produces better outcomes than carrier-direct or single-plan enrollment processes.

What the ANOC Is — and What It Isn’t

The Annual Notice of Change is a legally required document — CMS mandates that all Medicare Advantage and Part D plan sponsors send it to enrolled members by September 30 of each year. Its specific legal purpose is to notify beneficiaries of changes to their plan’s coverage, costs, and benefits that will take effect on January 1 of the following year. The ANOC is structured as a comparison document: it presents the current year’s terms alongside the upcoming year’s terms in a side-by-side format that is designed to make changes visible and identifiable without requiring the beneficiary to remember exactly what their current year’s terms were or to locate the original enrollment materials from the prior year’s AEP.

What the ANOC is not: it is not the Evidence of Coverage, which is a comprehensive document describing all plan terms in full detail. The EOC is typically much longer than the ANOC and serves as the complete contract reference for all plan provisions. The ANOC contains only what has changed — it does not describe the full plan in exhaustive detail. If something is not mentioned in the ANOC, it can generally be understood as unchanged for the coming year. The ANOC is also not a marketing document from your carrier — it does not encourage you to stay with your current plan or switch to a different one. It is a neutral, legally required disclosure document whose content is standardized by CMS guidelines, not crafted by your carrier’s marketing team. Finally, the ANOC is not a bill or invoice — it does not require payment or a signed response. It requires only that you read it and, if the changes it describes do not serve your interests, act during the Annual Election Period before December 7.

Who Receives an ANOC and Who Doesn’t

The ANOC applies exclusively to Medicare Advantage (Part C) plan enrollees and Medicare Part D prescription drug plan enrollees. If you are enrolled in both a Medicare Advantage plan that includes drug coverage (called an MA-PD) and a standalone Part D drug plan, you will receive ANOCs from each plan you are enrolled in. If you are enrolled in a standalone Part D drug plan alongside Original Medicare, you will receive an ANOC from your Part D plan. You will not receive an ANOC from Original Medicare itself — Medicare Parts A and B do not have the same annual refiling structure as Medicare Advantage and Part D plans.

Medicare Supplement (Medigap) policyholders do not receive ANOCs. This is one of the structural differences between Medicare Supplement and Medicare Advantage coverage that many beneficiaries do not fully understand. Medicare Supplement plans standardize their benefits by plan letter designation — Plan G, for example, provides the same defined set of benefits regardless of which insurance carrier issues the policy. While Medigap premiums do change over time (carriers can and do increase premiums, and age-based increases apply under most rating methods), the standardized benefit structure of Medigap plans does not change annually in the way that Medicare Advantage plan benefits, networks, and formularies do. A Medigap policyholder’s coverage for next year is defined by the same standardized benefit structure as their current year’s coverage. This is why Medigap enrollees do not receive ANOCs — there is no structured year-to-year benefit change to disclose. For a full comparison of how these plan types differ structurally, our resource on Medicare Advantage vs. Medicare Supplement covers this distinction in depth and helps clarify which type of coverage you currently have if you are uncertain.

When the ANOC Arrives and Why the Timing Is Deliberate

CMS requires that plans send the ANOC to enrolled members by September 30 of each year. In practice, many beneficiaries receive their ANOC in August or early September — before the September 30 deadline — though some arrive closer to the deadline. The September delivery window is not arbitrary. It gives beneficiaries a minimum of approximately two weeks to receive and review the document before the Annual Election Period opens on October 15. CMS calibrated this timeline to ensure that beneficiaries have actionable information about their coming-year plan terms before the window for making changes opens, rather than discovering changes only after January 1 when it is too late to act without a qualifying Special Enrollment Period.

The ANOC should be recognized when it arrives — it typically comes as a packet or envelope from your current Medicare Advantage or Part D plan carrier, labeled with language like “Important Plan Information for Next Year” or “Annual Notice of Change.” It can be easy to mistake for marketing mail, particularly during September and October when Medicare marketing season produces a high volume of plan-related materials in the mailbox. The key distinguishing feature is that the ANOC comes from your current plan carrier and includes a side-by-side comparison of current and upcoming year terms — it is about what your existing plan is doing, not about a different plan’s solicitation. If you have opted into electronic delivery through your plan’s member portal, the ANOC may be delivered electronically rather than by mail. If October arrives and you have not received your ANOC, contact your plan carrier directly to request a copy — failing to receive it does not extend the AEP deadline or create an exception to plan change rules.

ANOC Key Sections and What to Review in Each

ANOC content, formatting, and specific section organization vary by carrier and plan type. Medicare plan terms change annually; all figures in your ANOC reflect the specific plan’s filed terms for the upcoming year and should be verified through your plan documents and at Medicare.gov. Medicare plan rules and structures are subject to regulatory change. Consult a licensed Medicare specialist before making any plan change decision.

Drug Formulary Changes — The Most Consequential Section for Most Beneficiaries

For the majority of Medicare beneficiaries who take regular prescription medications, the drug formulary section of the ANOC is the single most important section to review with care. Medicare Advantage and Part D plans structure their drug coverage through a formulary — a list of covered medications organized into tiers, with different cost-sharing amounts applying at each tier. A Tier 1 medication (typically preferred generics) carries the lowest copay or coinsurance. A Tier 3 or Tier 4 medication (typically preferred brands or non-preferred drugs) carries substantially higher cost-sharing. A Tier 5 specialty medication can carry coinsurance rather than flat copays, producing very high out-of-pocket costs even for a single monthly fill.

Plans refile their formularies annually and have the authority to move medications between tiers, add new medications, remove medications, add prior authorization requirements, implement step therapy, or impose quantity limits on any drug. A medication that was covered at Tier 2 this year may move to Tier 3 or Tier 4 next year — increasing the monthly copay significantly with no requirement for the carrier to notify the beneficiary other than through the ANOC. A medication that required no prior authorization this year may require it next year, adding administrative burden and potential coverage delays. A medication may be removed from the formulary entirely, requiring the beneficiary to either switch to an alternative drug their physician approves or pay full price for the original medication. The ANOC’s formulary section identifies these changes — but reading it requires checking each medication individually rather than skimming past the drug section. For beneficiaries on multiple medications or on high-cost specialty drugs, this review can save hundreds or thousands of dollars annually by identifying a plan change that provides better formulary coverage. The Inflation Reduction Act established an annual out-of-pocket cap for Part D drug costs, eliminating the previous catastrophic exposure for very high-cost medications — this structural protection exists independently of any single plan’s formulary design and applies regardless of which plan a beneficiary is enrolled in.

Provider Network Changes — When Access to Care Is Affected

Medicare Advantage plans operate within defined provider networks — lists of physicians, specialists, hospitals, and other facilities that have contracted with the plan to provide services at negotiated rates. In-network care produces the cost-sharing terms described in the plan’s benefit summary. Out-of-network care — if covered at all, depending on whether the plan is an HMO or PPO — produces higher cost-sharing and in some cases is not covered except in emergency situations. Provider networks are not static. Physicians and hospital systems negotiate new contracts, end existing ones, or change their network participation across multiple plans annually. A physician who was in-network this year may have ended their participation with your plan, and the ANOC is where that change is disclosed — specifically in the provider network section or the service area section.

The network change that creates the most immediate planning problem is when a beneficiary’s primary care physician, managing specialist, or primary hospital exits the plan network for the coming year. If you are managing a chronic condition with a specific specialist who knows your history, or if you have a planned procedure at a specific hospital scheduled for the following year, discovering a network change after January 1 may mean either paying out-of-network costs or seeking a new in-network provider quickly. Both outcomes are avoidable if the ANOC is reviewed before December 7. The practical verification step is to check each current provider’s participation in the plan’s coming-year network — not just whether the physician’s practice is listed, but whether the specific physician within a group practice is in-network, since network participation can vary within a practice. This verification can be done through the plan’s online provider directory, by calling the plan directly, or by having your physician’s billing office confirm participation for the coming year.

The Annual Election Period — Your Action Window

The Annual Election Period (AEP) runs from October 15 through December 7 each year. It is the broadest enrollment and change opportunity available to Medicare beneficiaries, and it is the period during which the ANOC’s content is most actionable. During AEP, beneficiaries enrolled in Medicare Advantage can switch to a different Medicare Advantage plan, return to Original Medicare with or without a standalone Part D plan, or change their Part D drug plan. Beneficiaries enrolled in Original Medicare can join a Medicare Advantage plan or enroll in a new Part D plan. All changes made during AEP take effect January 1 of the following year. No special qualifying event or reason is required — the AEP is an open window that does not require justification for plan changes.

The AEP is not unlimited in scope. It does not include the ability to switch between Medicare Supplement (Medigap) policies without medical underwriting in most states. If you are considering a move from Medicare Advantage back to Original Medicare and want to add Medigap coverage, that decision requires understanding your state’s underwriting rules — some states have guaranteed issue protections for Medigap enrollment after leaving Medicare Advantage, while others do not. Our resource on Medicare Advantage vs. Medicare Supplement covers this distinction in detail. The practical implication is that the AEP decision window for Medigap changes is not as simple as the MA-to-MA comparison. If returning to Original Medicare with Medigap is a consideration based on your ANOC review, that evaluation should include understanding your eligibility and underwriting status before the AEP deadline. A second opinion on your Medicare coverage through an independent specialist can clarify these options before December 7.

The Medicare Advantage Open Enrollment Period — A More Limited Window

The Medicare Advantage Open Enrollment Period (MA OEP) runs from January 1 through March 31 each year. Unlike the AEP, the MA OEP is more limited in scope — it allows beneficiaries who are already enrolled in a Medicare Advantage plan to switch to a different Medicare Advantage plan or to return to Original Medicare, but it does not allow unrestricted movement between all Medicare plan types. Specifically, the MA OEP cannot be used to enroll in a Medicare Advantage plan for the first time from Original Medicare, to switch between standalone Part D drug plans, or to address most Medigap enrollment situations. The MA OEP exists as a correction mechanism for beneficiaries who made a plan change during AEP and subsequently discovered they wanted a different option, or who experienced their ANOC-disclosed plan changes taking effect on January 1 and decided they were not acceptable.

For beneficiaries who receive their ANOC in September, review it carefully, and act during the October 15 through December 7 AEP window, the MA OEP is typically not needed — the AEP provides the most flexibility for addressing ANOC-driven concerns. Beneficiaries who missed the AEP or who discover post-January 1 issues that were disclosed in the ANOC but not fully appreciated until experienced in real-life claims may find that the MA OEP offers some relief, but its narrower scope means it cannot address all situations that the AEP could have. This temporal limitation underscores the importance of reviewing the ANOC before December 7 rather than waiting to see how the plan changes actually affect your healthcare access and costs in the new year.

What Happens If You Don’t Review Your ANOC

If you take no action during the Annual Election Period, you will automatically remain enrolled in your current Medicare Advantage or Part D plan with the updated terms disclosed in your ANOC. Your premiums for the new year will begin, your new cost-sharing terms will apply to all services and prescriptions from January 1, your updated provider network will determine which physicians and facilities are in-network, and your updated formulary will determine which drugs are covered at which tier. None of these changes require your agreement — you agreed to the possibility of annual changes when you enrolled in the plan, and the ANOC satisfies the carrier’s legal obligation to notify you before those changes take effect.

The financial consequences of missing ANOC changes depend entirely on what changed. A year in which premiums, cost-sharing, network, and formulary are unchanged or improved is a year where auto-renewal costs nothing additional. A year in which your maximum out-of-pocket increased significantly, your primary specialist left the network, your most expensive medication moved to a higher tier, or a planned procedure at your preferred hospital became out-of-network is a year where the failure to review the ANOC and act during AEP can produce thousands of dollars in avoidable costs. Because Medicare plans file their terms with CMS annually and carriers set those terms based on their own actuarial and competitive analysis — not based on any individual beneficiary’s satisfaction — there is no guarantee of continuity in any specific plan element from one year to the next.

IRMAA, Medicare Premiums, and the Broader Income Picture

The ANOC addresses plan-level premiums and cost-sharing — what your specific Medicare Advantage or Part D plan will charge in the coming year. A separate but related dimension of Medicare premium planning that deserves attention alongside the ANOC review is the Income-Related Monthly Adjustment Amount (IRMAA), which CMS applies to Medicare Part B and Part D premiums for beneficiaries whose modified adjusted gross income exceeds defined thresholds. IRMAA surcharges are determined based on income reported on tax returns from two years prior, and they can add meaningfully to the base Medicare premium for higher-income retirees. Our resource on IRMAA planning strategies covers how to anticipate, appeal, and plan around these income-related premium adjustments.

The intersection of IRMAA planning and the broader retirement income picture is one of the reasons that Medicare decisions do not exist in isolation from retirement financial planning. Higher taxable income — from RMDs, Social Security, annuity distributions, or investment sales — can affect Medicare premiums in subsequent years through the IRMAA mechanism. Resources covering the RMD framework after SECURE 2.0, key retirement considerations, and how annuities function as retirement investments are all relevant context for understanding how income decisions produce Medicare cost implications that compound over time. When predictable income from guaranteed sources covers essential expenses — including healthcare premiums — annual ANOC changes become less financially destabilizing because the income floor is not subject to the same variability as the plan terms themselves. The IRA to annuity transfer resource covers how some retirees restructure their retirement income streams to create this predictability alongside their Medicare planning.