Two Medicare Documents That Arrive Before Open Enrollment: The ANOC and the EOC

The Mail That Shows Up Before You Can Act

Every fall, people enrolled in Medicare Advantage and Medicare Part D prescription drug plans receive a wave of paperwork from their insurers. It tends to arrive weeks before Medicare's Open Enrollment period begins on October 15, which can be confusing. Why send plan information before anyone can actually make a change?

The answer is straightforward once you know what the documents are. Medicare requires plans to give members a clear picture of the coming year before the decision window opens, so there is time to read, compare, and think. Two documents do most of that work: the Annual Notice of Change and the Evidence of Coverage. They are not the same thing, and they do not arrive at the same time.

The Annual Notice of Change (ANOC)

The Annual Notice of Change, often shortened to ANOC, is the document that highlights what is different about your plan for the upcoming year. According to Medicare, it covers changes in a plan's coverage, costs, provider networks, and service area, along with other adjustments that will take effect the following January.

For 2027 coverage, Medicare says plans must send the ANOC by September 30. That timing is deliberate. It lands in mailboxes before Open Enrollment starts, giving members a head start on understanding whether their plan still fits their needs.

Think of the ANOC as a summary of differences. It is designed to answer a single question: what is changing? If your monthly premium is going up, if a medication you take is moving to a different cost tier, if your doctor is leaving the network, or if the plan is no longer offered in your county, the ANOC is where that information is meant to appear. Because it focuses on changes rather than the full rulebook, it is usually shorter and easier to skim than the second document.

The Evidence of Coverage (EOC)

The Evidence of Coverage, or EOC, is the fuller reference document. Medicare describes it as providing details on what the plan covers and what members pay in the coming year. For 2027 coverage, plans must send the EOC by October 15, the same day Open Enrollment begins.

Where the ANOC tells you what is different, the EOC tells you how the plan works in full. It spells out benefits, rules, costs, and the rights and responsibilities that come with membership. If you want to know exactly how a specific service is covered, what your share of the cost will be, or the conditions attached to a benefit, the EOC is the place to look. It is longer and more detailed precisely because it is meant to be the complete description rather than a highlight reel.

Why the Two Dates Matter

The staggered timing is easy to miss, but it follows a logic. The ANOC arrives first, by September 30, so members can see the changes before the decision period opens. The EOC follows by October 15, coinciding with the start of Open Enrollment, so the detailed reference is in hand when comparisons begin.

Put simply, the ANOC gives you an early warning about what is changing, and the EOC gives you the full text to consult once you are ready to weigh your options. Reading them in that order can make the process feel less overwhelming.

How to Read Them Side by Side

A practical approach is to start with the ANOC. Because it focuses on changes, it can quickly tell you whether anything meaningful has shifted since last year. If your premium, deductible, drug coverage, or network looks different in a way that affects you, that is your signal to dig deeper.

When something in the ANOC catches your attention, the EOC is where you turn for the complete explanation. Say the ANOC notes a change to how a certain type of care is covered. The EOC will describe the specific rules, the costs involved, and any limits that apply. Used together, the two documents move you from a quick scan of what is new to a full understanding of how the plan will actually operate.

Keeping the Fall Calendar Straight

The Medicare fall season has a rhythm. Plan information begins arriving before Open Enrollment opens. The ANOC is due by September 30 for 2027 coverage, and the EOC is due by October 15, the same day the enrollment window begins. Open Enrollment then runs through early December, giving members a defined period to make changes if they choose.

Knowing that these are two different documents with two different purposes takes much of the mystery out of the mail. One highlights what is changing. The other provides the fuller description of next year's coverage. That distinction alone makes the autumn Medicare calendar considerably easier to read.