Your Medicare Explanation of Benefits (EOB) arrives in the mail each month and is one of the most useful documents you receive as a Medicare enrollee. Most people glance at it and toss it aside. That is a mistake. Your EOB tells you exactly what was billed to your plan, what your plan paid, and what you owe. It is also one of the best tools for catching billing errors before they become your problem.
This guide walks through every section of a Medicare EOB, explains the difference between an EOB and a Medicare Summary Notice, and shows you what to do if something looks wrong.
What Is a Medicare Explanation of Benefits?
An Explanation of Benefits is a statement your Medicare plan sends after you use a covered medical service or fill a prescription. It is not a bill. It is a record showing how a claim was processed.
Who gets an EOB depends on which type of Medicare you have:
- Medicare Advantage (Part C): Your private insurance plan sends you an EOB after you receive services.
- Part D (prescription drug coverage): Your drug plan sends a monthly EOB summarizing all prescriptions filled.
- Original Medicare (Parts A and B): You receive a Medicare Summary Notice (MSN) instead of an EOB. The MSN comes from the federal government, not a private insurer.
If you have both Original Medicare and a Medigap (supplemental) policy, you will receive an MSN from Medicare and a separate EOB from your Medigap insurer. Both documents together show the full picture of what was paid and what you owe.
Medicare EOB vs. Medicare Summary Notice
These two documents serve the same basic purpose but come from different sources and arrive on different schedules.
| Feature | Medicare EOB | Medicare Summary Notice (MSN) |
|---|
| Who sends it | Private Medicare Advantage or Part D plan | Federal government (Medicare) |
| Who receives it | Medicare Advantage and Part D enrollees | Original Medicare enrollees |
| How often | Monthly (some plans vary) | Quarterly |
| Format | Varies by plan | Standardized format |
| Covers prescriptions | Yes (Part D EOB) | No (Part A and B services only) |
| Shows coverage stage | Yes (Part D EOB) | No |
If you are unsure which document you receive, check the sender. An EOB comes from a company like Humana, Aetna, or UnitedHealthcare. An MSN comes directly from Medicare.gov or CMS (Centers for Medicare and Medicaid Services).
How to Read Your Medicare Advantage EOB
Medicare Advantage EOBs vary by insurer, but they all contain the same core information. Here is what to look for in each section.
Section 1: Member and Plan Information
The top of the first page identifies you and your plan. Verify:
- Your name and member ID are correct
- The plan name and year match your current enrollment
- The date range the EOB covers
An error in your member ID can cause claims to be denied or paid incorrectly.
Section 2: Claim Summary Table
This is the most important section. It typically appears as a table with one row per claim. Each row shows:
| Column | What It Means |
|---|
| Date of service | When you received care |
| Provider name | Doctor, hospital, or facility |
| Service description | What was provided (may use medical codes) |
| Amount billed | What the provider charged |
| Plan discount | Amount reduced by your plan's negotiated rate |
| Amount plan paid | What your insurance covered |
| Your responsibility | What you owe the provider |
| Reason code | A code explaining adjustments or denials |
Look at the "Amount billed" column first. If a provider billed for a service you did not receive, that is a red flag. Then check "Your responsibility" to see what you actually owe.
Section 3: Deductible and Out-of-Pocket Tracker
Most EOBs include a running tally of your spending toward your deductible and annual out-of-pocket maximum. In 2026, Medicare Advantage plans must cap out-of-pocket costs at $9,350 for in-network services. Once you hit that limit, your plan covers 100% of covered services for the rest of the year.
This tracker helps you know exactly where you stand without having to add up receipts yourself.
Section 4: Reason Codes and Adjustment Codes
Every line item on an EOB has a code explaining why a claim was paid, reduced, or denied. These codes are listed in a legend at the back of the document. Common ones include:
- CO-45: Charge exceeds fee schedule or maximum allowable amount (normal adjustment)
- PR-1: Deductible amount (you owe this until your deductible is met)
- PR-2: Coinsurance (your percentage share)
- CO-4: Service inconsistent with diagnosis (possible denial)
- CO-197: Precertification/authorization was absent (possible denial)
If a claim was denied, the reason code tells you why. That is the starting point for any appeal.
How to Read Your Part D EOB
Your Part D drug plan sends a monthly EOB summarizing every prescription you filled. This document also tracks your spending through the Part D coverage stages, which changed significantly in 2026.
2026 Part D Coverage Stages
| Stage | When It Applies | What You Pay |
|---|
| Deductible phase | Before meeting your deductible | Up to 100% of drug costs (max deductible: $615 in 2026) |
| Initial coverage | After deductible until $2,100 out-of-pocket | 25% coinsurance for all covered drugs |
| Catastrophic coverage | After $2,100 out-of-pocket | $0 for the rest of the year |
The $2,100 out-of-pocket cap is new in 2026 under the Inflation Reduction Act changes. Previously, there was a coverage gap (often called the "donut hole") that required you to pay more. That structure no longer exists. Your monthly Part D EOB shows your current coverage stage and how close you are to the catastrophic threshold.
What to Check on Your Part D EOB
Each prescription entry shows:
- Drug name and dosage
- Date filled and pharmacy
- Days' supply
- Total drug cost
- What the plan paid
- What you paid
- Amounts credited toward your out-of-pocket total
Verify that every prescription listed matches what you actually filled. If a drug appears that you did not pick up, contact your pharmacy first, then your plan if the issue is not resolved.
How to Read a Medicare Summary Notice (MSN)
If you have Original Medicare, your MSN arrives quarterly. It covers all claims processed by Medicare during a three-month period.
The MSN is organized by claim type: Part A (hospital) and Part B (medical). For each claim, you see:
- Provider name and service date
- Service billed
- Amount billed by provider
- Medicare-approved amount (the negotiated rate)
- Medicare paid (typically 80% of the approved amount for Part B)
- You may be billed (typically 20% of the approved amount)
One important note: if you have a Medigap policy, you likely owe less than what the MSN shows in the "You may be billed" column. Your Medigap plan pays some or all of that amount, and will send its own EOB showing what it covered.
Step-by-Step: How to Review Your EOB for Errors
Medicare billing errors are more common than most people realize. Duplicate charges, services that were never provided, and incorrect billing codes can all appear on your EOB. Follow these steps each time a new EOB arrives.
Step 1: Match services to your records
Keep a simple log of every doctor visit, procedure, or prescription you received. Compare your log to the services listed on your EOB. Any service you do not recognize needs investigation.
Step 2: Check provider names and dates
Confirm that the provider name and date match what your appointment records show. An incorrect date can sometimes indicate a duplicate claim.
Step 3: Review reason codes for denials
If any line item shows $0 paid by your plan, look at the reason code. Some denials are automatic errors that resolve with a phone call. Others require a formal appeal.
Step 4: Verify your cost-sharing amounts
Compare what the EOB says you owe to what you actually paid at the time of service. If there is a discrepancy, contact your provider's billing office before paying any new invoices.
Step 5: Check the deductible and out-of-pocket tracker
Make sure amounts credited toward your deductible and out-of-pocket maximum are accurate. An error here can cause you to overpay throughout the year.
What to Do If You Find an Error
For billing code errors: Call your provider's billing office first. Many errors are simple coding mistakes that can be corrected with a rebill to Medicare. This is the fastest resolution.
For plan coverage disputes: Contact your Medicare Advantage or Part D plan directly. Use the member services number on your insurance card. Ask them to explain the reason code and whether the service qualifies for coverage.
For claims you believe should be covered: File a formal appeal. The appeal timeline and process depend on your plan type.
Medicare Appeals Process (2026)
| Level | Deadline to File | Decision Timeframe |
|---|
| Level 1: Redetermination | 120 days from EOB date | 60 days (non-urgent) |
| Level 2: Reconsideration (independent review) | 180 days from Level 1 decision | 60 days |
| Level 3: ALJ Hearing (requires $200+ at stake) | 60 days from Level 2 decision | 90 days |
| Level 4: Medicare Appeals Council | 60 days from Level 3 decision | 90 days |
| Level 5: Federal Court (requires $1,960+ at stake) | 60 days from Level 4 decision | Varies |
Always file appeals in writing and keep copies of everything you send. Certified mail with return receipt provides documentation if there are later disputes about timing.
Medicare Savings Programs: Help With Costs
If reviewing your EOB has made you realize your Medicare costs are a burden, you may qualify for Medicare Savings Programs (MSPs). These are state-run programs that help pay Medicare premiums, deductibles, and coinsurance for people with limited income and assets.
There are four types of Medicare Savings Programs:
| Program | Who It Helps | What It Covers |
|---|
| Qualified Medicare Beneficiary (QMB) | Income up to 100% FPL | Part A and B premiums, deductibles, coinsurance, and copays |
| Specified Low-Income Medicare Beneficiary (SLMB) | Income 100-120% FPL | Part B premium only |
| Qualifying Individual (QI) | Income 120-135% FPL | Part B premium only (funding limited) |
| Qualified Disabled and Working Individual (QDWI) | Disabled working individuals | Part A premium only |
For 2026, the federal poverty level for a single person is $15,650 per year. A single person earning up to approximately $21,128 per year (135% FPL) could qualify for some form of MSP assistance.
MSP enrollment also automatically qualifies you for Extra Help with Part D costs, which lowers your prescription drug copays significantly.
To check if you qualify, use our free screener at benefitsusa.org/screener. You can also contact your state Medicaid office directly.
Keeping Your EOBs
Hold onto your EOBs for at least one year. You may need them to:
- Dispute a bill from a provider
- Verify that your secondary insurance paid correctly
- Confirm your spending toward deductibles and out-of-pocket limits
- File a formal Medicare appeal
Digital copies work just as well as paper. Many Medicare Advantage plans offer online portals where you can access EOBs going back several years.
Frequently Asked Questions
Is a Medicare EOB the same as a bill?
No. An EOB is a record of how a claim was processed. It shows what was billed, what your plan paid, and what you may owe, but the actual bill comes from your provider separately. Never pay based on an EOB alone. Wait for an invoice from your doctor or facility, then compare it to your EOB before paying.
How often will I receive an EOB?
Medicare Advantage plans typically send an EOB monthly. Part D plans send one monthly as well, covering all prescriptions filled that month. Original Medicare enrollees receive an MSN quarterly, summarizing all claims from the past three months.
What does it mean when my EOB shows $0 paid by my plan?
A $0 payment could mean the claim was denied, it applied to your deductible, or the service was not covered under your plan. Look at the reason code in the same row to understand why. If the denial seems incorrect, contact your plan or file a redetermination request.
Can I get my Medicare EOB online?
Yes. Most Medicare Advantage and Part D plans offer online member portals where you can view and download EOBs. Log into your plan's website or app and look for "claims" or "EOB" in your account settings. Original Medicare enrollees can view their MSN through MyMedicare.gov.
What if a service I received is not on my EOB?
It could mean the claim has not been processed yet, or there was a billing error on the provider's side. Wait a few weeks and check again. If it still does not appear, call your provider to confirm they billed Medicare, then contact your plan if the issue continues.
What is the Part D out-of-pocket cap in 2026?
In 2026, the maximum out-of-pocket limit for Part D prescription drug costs is $2,100. Once you reach this threshold, you pay nothing for covered drugs for the rest of the calendar year. Your monthly Part D EOB tracks your progress toward this limit.
How do I appeal a denied Medicare claim?
Start with a Level 1 Redetermination request. Contact your plan or Medicare (for Original Medicare) within 120 days of receiving the EOB or MSN. Submit your request in writing and include any supporting documents such as a physician's letter or medical records. Your plan must respond within 60 days for standard appeals.
Who qualifies for Medicare Savings Programs?
Medicare Savings Programs help people with limited income cover Medicare costs. Income limits vary by program and state, but generally a single person earning up to about 135% of the federal poverty level ($21,128 in 2026) may qualify for some assistance. Use the free eligibility screener at benefitsusa.org/screener to find out if you qualify.
