How Do I Read My Parent's Medicare Letter? MSN, EOB & Denials (2026)

Most Medicare mail is informational, but three letters carry deadlines: the Annual Notice of Change (arrives by September 30, plan changes take effect January 1), denial notices (65 days to appeal a Medicare Advantage denial, 120 days for Original Medicare), and Social Security IRMAA letters (60 days to appeal). The Medicare Summary Notice and plan Explanation of Benefits are not bills, they are claim summaries you should skim for errors (Medicare.gov).

When my mother-in-law started handing me her Medicare mail in a rubber-banded stack, I sorted it into three piles: things that needed action, things worth filing, and things that went straight to the shredder. It took me a year of mistakes to sort confidently. The worst mistake was nearly missing an appeal deadline because a denial notice looked like every other piece of plan mail.

This guide is that sorting system, updated for 2026, what each letter is, what it is quietly telling you, and which ones have a clock running.

Which Medicare letters actually matter?

Four kinds of Medicare mail deserve immediate attention: denial notices (appeal deadlines run from the date on the letter), the Annual Notice of Change each September, IRMAA determination letters from Social Security, and premium bills. Claim summaries, MSNs and EOBs, matter too, but as error-checks, not emergencies.

Here is the caregiver's triage table:

Letter	Who sends it	What it means	Deadline?
Medicare Summary Notice (MSN)	Medicare	Claim summary, Original Medicare	Appeal within 120 days if a claim was denied
Explanation of Benefits (EOB)	MA or Part D plan	Claim summary, private plan	Check for errors; denials arrive separately
Annual Notice of Change (ANOC)	MA or Part D plan	Next year's costs and coverage	Act by December 7 if the plan got worse
Denial notice	Plan or Medicare	Care or payment refused	65 days (MA) / 120 days (Original Medicare)
IRMAA letter	Social Security	Premium surcharge based on income	60 days to appeal; use Form SSA-44
Medicare Premium Bill (CMS-500)	Medicare	Actual bill for Part A/B premiums	Pay by the due date
Medicare & You handbook	Medicare	Annual reference book	None, keep it

Everything else, plan newsletters, wellness program flyers, marketing from other insurers, can usually be recycled. The rest of this guide takes the big ones in order.

What is a Medicare Summary Notice and how do I read it?

The Medicare Summary Notice (MSN) is the claim summary for Original Medicare. It is not a bill. Medicare mails it at least twice a year, your parent gets one every 6 months in which they received Part A or Part B services, and it shows what providers billed, what Medicare paid, and the maximum your parent may owe.

The wording matters because the MSN's own header says it plainly: "It's not a bill" (Medicare.gov). Any provider bill should arrive separately and should match the "maximum you may owe" column on the MSN. When a provider's bill exceeds that figure, call the provider before paying, billing errors in this direction are common.

Read an MSN in three passes:

1. The claims list. Does every line correspond to a visit your parent actually had? Unfamiliar providers or dates can signal billing errors or fraud, report suspicious entries to 1-800-MEDICARE.
2. The "denied" column. Any service Medicare did not approve appears here, with instructions on the notice for filing an appeal. Your parent has 120 days from receiving the MSN to request a redetermination (CMS).
3. The deductible tracker. The MSN shows progress toward the $283 Part B deductible in 2026, which explains early-year bills that surprise many families.

One practical upgrade: paper MSNs arrive on a 6-month cycle, but electronic MSNs arrive monthly whenever there is a processed claim. Sign your parent up through their secure account at Medicare.gov, for a caregiver, a monthly email beats a semiannual envelope for catching problems early.

How is an EOB different from an MSN?

An Explanation of Benefits (EOB) is the private-plan version of the MSN. If your parent has Medicare Advantage or a standalone Part D plan, the plan, not Medicare, sends an EOB, typically monthly when there are claims. Like the MSN, it is not a bill; it shows what the plan paid and what your parent owes providers.

The practical differences for a caregiver:

• Source. EOBs come from the insurance company (UnitedHealthcare, Humana, Aetna, and so on), so they carry the plan's branding, which also makes them easy to confuse with the plan's marketing mail. Look for the words "Explanation of Benefits."
• Drug EOBs track the $2,100 cap. Part D EOBs show cumulative out-of-pocket drug spending. In 2026, once that figure reaches $2,100, your parent pays $0 for covered drugs the rest of the year, the EOB is where you verify the plan is counting correctly.
• Denials work differently. An EOB line showing a reduced or refused payment is a signal, but the formal denial arrives as a separate notice with appeal rights (next section). Do not appeal from the EOB alone; wait for or request the actual denial notice.

Keep at least one year of EOBs and MSNs. Tax preparers, Medicaid applications, and appeal filings all occasionally need them.

What is the Annual Notice of Change and why does September matter?

The Annual Notice of Change (ANOC) arrives from your parent's Medicare Advantage or Part D plan by September 30 and lists every change to premiums, copays, drug coverage, and provider networks taking effect January 1 (Medicare.gov). It is the single most consequential, and most discarded, letter of the year.

Plans redesign themselves annually. A drug can move to a higher tier, a doctor can drop out of network, a $0 premium can become $40, and none of it requires your parent's consent, only this notice. The ANOC is the formal warning, and the window to act on it is Medicare open enrollment, October 15 through December 7.

Read the ANOC side-by-side comparison chart (plans must show this year versus next year) and check three things against your parent's actual usage:

1. Their drugs. Formulary tier changes and new prior-authorization requirements.
2. Their doctors and hospital. Network status for next year.
3. The maximum out-of-pocket. In 2026 the federal ceiling is $9,250 in-network, but the average plan sets about $5,421, a big jump in your parent's plan is a reason to shop (KFF).

If no ANOC has arrived by early October, contact the plan, Medicare requires it to be sent (Medicare.gov).

What does a denial notice look like and what are the deadlines?

A Medicare Advantage denial arrives as a "Notice of Denial of Medical Coverage (or Payment)" and starts a 65-day appeal clock. An Original Medicare denial appears on the MSN and allows 120 days. Both deadlines run from the notice date, and the majority of appealed MA denials are overturned, so appealing is usually worth it.

The numbers argue for persistence: Medicare Advantage insurers issued 4.1 million prior-authorization denials in 2024, only 11.5% were appealed, and 80.7% of appeals succeeded (KFF). Most families who fight, win. Most families never fight.

The deadlines, precisely:

• Medicare Advantage: 65 days from the denial notice to request reconsideration. The plan must decide within 30 days (standard) or 72 hours (expedited); if it upholds the denial, the case is automatically forwarded to an independent reviewer (CMS).
• Part D drug denials: 65 days to request a redetermination from the plan (CMS).
• Original Medicare: 120 days from the MSN to request redetermination; the contractor has 60 days to decide (CMS).

The full playbook, including expedited appeals during a hospital discharge, is in our guide to appealing a Medicare denial for a parent.

Which letters are junk mail or scams?

Real Medicare mail comes from Medicare, Social Security, or your parent's own plan, and Medicare does not call, text, or email asking for a Medicare number or payment. Glossy mail promising "$2,880 flex cards," "free groceries," or urging your parent to call an 800 number to "activate new benefits" is marketing or fraud.

Distinguishing features of legitimate mail: it names your parent's actual plan, it references specific claims or coverage, and it never asks for a Social Security or Medicare number your plan already has. Marketing mail is legally required to say it is marketing, look for fine print like "not affiliated with the federal Medicare program."

Two specific patterns to warn a parent about, documented by the AARP Fraud Watch Network and the FTC:

• Flex-card bait. Ads exaggerate prepaid benefit cards to harvest personal information. Real benefit cards come from your parent's own plan without a phone call.
• Imposter calls following mail. Scammers time calls to open enrollment, claiming to "verify" information from a letter. Medicare initiates almost no phone contact; hang up and call 1-800-MEDICARE directly.

Shred anything with your parent's Medicare number rather than recycling it, the number is as valuable as a credit card.

How do I get Medicare to discuss my parent's letters with me?

Medicare will not discuss your parent's claims with you until your parent gives permission, verbally by joining a call to 1-800-MEDICARE, or durably by filing Form CMS-10106, the Authorization to Disclose Personal Health Information. File the form once and you can call about MSNs, claims, and appeals without your parent on the line.

For a one-off question, the fastest route is a three-way call: your parent joins, tells the representative to speak with you, and the conversation proceeds. For ongoing caregiving, download Form CMS-10106 and mail it to the address in the instructions; Medicare will then talk to you directly about anything the authorization covers (Medicare.gov).

Note that this authorization covers conversations with Medicare, it does not make you a legal decision-maker, and Medicare Advantage plans have their own authorization forms. The distinctions are mapped in our guide to power of attorney versus Medicare authorized representative.