7 min read · Last updated October 14, 2026
- Medicare Advantage and Part D plans must send enrollees an Annual Notice of Change (ANOC) each fall, and the National Council on Aging states plainly that “you should get your Medicare ANOC by Sept. 30.”
- The ANOC covers changes effective the following January 1, including premium, deductible, drug-tier copay, and provider-network changes, per Medicare.gov’s own description of the notice.
- Medicare’s Open Enrollment Period, also called the Annual Enrollment Period (AEP), runs October 15 through December 7, giving roughly ten weeks between the ANOC deadline and the close of the window to act on it.
- Medicare Advantage organizations operate under federal disclosure rules codified in the Code of Federal Regulations (CFR) at 42 CFR 422.111, which the Centers for Medicare & Medicaid Services (CMS) enforces directly.
Medicare Advantage and Part D plans are required to mail you an Annual Notice of Change by September 30 each year, spelling out your new premium, deductible, drug-tier costs, and any provider-network changes effective the following January 1.
In this article
- What the Medicare Annual Notice of Change letter must tell you
- Why the September 30 date matters more than it looks
- Why last year’s best plan can quietly stop being the right one
- Frequently asked questions
Every Medicare Advantage and Part D plan has to mail an Annual Notice of Change (ANOC) by September 30, and that single letter resets your costs for the entire year ahead before open enrollment even opens.
Earl Whitfield almost filed his unopened. His Medicare Advantage ANOC arrived in Scranton, Pennsylvania on September 29, the day before the deadline, in an envelope that looked identical to the plan’s usual monthly mailers.
Buried on page two, his go-to cholesterol medication had moved from Tier 2 to Tier 4 for the coming year, and his plan was adding a deductible it hadn’t charged before. He caught it only because his daughter asked to see the letter over dinner.
What the Medicare Annual Notice of Change letter must tell you
Medicare.gov describes the notice in plain terms: “your plan will send you a ‘Plan Annual Notice of Change’ (ANOC) each fall,” and “the ANOC includes any changes in coverage, costs, and more that will be effective in January.” The National Council on Aging is more specific about the deadline itself: “You should get your Medicare ANOC by Sept. 30.”
The letter is required for both Medicare Advantage plans and standalone Part D drug plans. It is not sent for Medigap, the supplement plans that fill gaps in Original Medicare, because federal law standardizes what those plans cover and their benefits don’t change from year to year the way Advantage and Part D benefits do.
Four things commonly change inside the letter, per the National Council on Aging’s own description: your premium (“may go up, stay the same, or even decrease”), your deductible (“it might be different next year”), your drug copays (“changes to the co-pays for medication in Tiers 1 through 5”), and your provider network (“if any of your doctors, hospitals, or pharmacies are leaving the network”).
The letter’s length is part of why people skip it. A combined Annual Notice of Change and Evidence of Coverage mailing can run dozens of pages, most of it unchanged boilerplate from the prior year.
The actual changes are usually concentrated in a short summary section near the front, often a single page or two, before the document repeats the plan’s full standing rules. Reading that one section first, rather than the whole packet cover to cover, catches most of what matters.
Why the September 30 date matters more than it looks
The ANOC deadline sits exactly 15 days before Medicare’s Open Enrollment Period, also called the Annual Enrollment Period (AEP), which the National Council on Aging states runs “Oct.15-Dec. 7.” That gap is not an accident. It is the window meant to give you time to read the letter, compare it against other plans, and switch before your current plan’s new terms take effect on January 1.
Medicare Advantage organizations operate under federal disclosure rules codified at 42 CFR 422.111, which require plans to give enrollees accurate, timely information about costs and coverage. CMS enforces that disclosure duty directly.
A second, separate window exists for people already on a Medicare Advantage plan: the Medicare Advantage Open Enrollment Period (MA OEP), which runs January 1 through March 31 each year. It only lets you make one plan change, and it isn’t a substitute for reading the September letter, since a network change discovered mid-year can leave you locked in long before that spring window ever opens. Someone who skips the ANOC and waits for the spring window still spends January, February, and part of March paying the higher cost the letter would have flagged months earlier.
The table below lines up the two dates against what’s actually at stake in between them.
| Date | What happens | What you can still do |
|---|---|---|
| By September 30 | Your plan mails the Annual Notice of Change | Read it in full, not just the first page |
| October 15 | Open Enrollment (AEP) begins | Switch plans if the changes don’t work for you |
| December 7 | Open Enrollment closes | Last day to make a change for January 1 |
| Best for | Anyone on Medicare Advantage or a standalone Part D plan, every year, regardless of whether last year’s plan seemed fine | |
Why last year’s best plan can quietly stop being the right one
Earl’s situation is the exact scenario the notice exists to catch. His plan hadn’t failed him in any obvious way over the prior year. The coming year’s version of the same plan, after the tier change and the new deductible, would have cost him meaningfully more for the same prescription, and he would not have known until the first January claim was rejected at the higher price.
Your Evidence of Coverage (EOC), the full plan rulebook, carries every detail behind the ANOC’s summary version. If a line in the notice is unclear, that document, or a call to the plan directly, has the full answer.
The ANOC’s job is to flag that something changed. Reading the rest is still yours to do before December 7 closes the window.
Earl’s own copay on the reclassified drug moved from a flat $10 a month under Tier 2 to roughly $85 a month once it landed in Tier 4, a difference of close to $900 over a full year on one prescription alone, the same kind of brand-name drug cost that can hit before Part D coverage even starts for someone else’s plan. He caught it with nearly ten weeks left before the AEP closed, enough time to compare his plan against two others serving his county and switch to one that kept the same drug at a lower tier. A reader who sets the letter aside until November, or later, may not have that much runway left to act on what it says.
Frequently asked questions
What should I do if my Annual Notice of Change never arrives by September 30?
Contact your plan directly. Medicare.gov’s own guidance states plainly: “If you don’t get this important document, contact your plan.” Don’t assume no letter means no changes.
Is the Annual Notice of Change the same document as the Evidence of Coverage?
No. The ANOC is a shorter summary of what’s changing for the new year. The Evidence of Coverage is the complete plan rulebook, covering everything the plan does and doesn’t pay for, in full detail.
Can I switch plans as soon as I read my Annual Notice of Change, or do I have to wait for October 15?
For most people, you have to wait for the Annual Enrollment Period, October 15 through December 7, to make a plan change effective the following January 1. Certain life events can open a Special Enrollment Period outside that window, but the ANOC itself doesn’t open one on its own.
Do Medigap supplement plans send an Annual Notice of Change too?
No. Medigap plans are standardized by federal law, so their covered benefits don’t change year to year, and they aren’t required to send this particular notice. Premiums on a Medigap plan can still change, but through a separate process.
If nothing in my Annual Notice of Change looks different, do I still need to read the whole letter?
Yes. Changes are sometimes isolated to a single drug tier or a small set of providers rather than the headline premium number, so a letter that looks unchanged at a glance can still carry a change that affects your specific prescriptions or doctors.
Compare Medicare plan options before December 7
See how your plan’s new costs stack up against other options available in your area this Annual Enrollment Period.
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