Understanding Your Medicare Explanation of Benefits (EOB)
You get mail from Medicare or your insurance company. Is it a bill? How much do you actually owe? Let me decode your Medicare Explanation of Benefits.
What Is an EOB?
EOB = Explanation of Benefits
It's NOT a bill—it's a summary showing:
What medical service you received
What the provider charged
What Medicare/your plan paid
What you owe (if anything)
Think of it as a receipt, not a bill.
Medicare Summary Notice (MSN)
If you have Original Medicare, you get a Medicare Summary Notice every 3 months.
Shows:
All Part A and Part B services used
What Medicare approved
What Medicare paid
What you may owe
Comes by mail (or view online at Medicare.gov)
Reading Your MSN Step-by-Step
Section 1: Services You Received
Columns:
Date: When you received service
Service: What was done (office visit, X-ray, etc.)
Provider: Doctor or facility name
Amount charged: What provider billed
Medicare-approved amount: What Medicare allows
Medicare paid: What Medicare actually paid (usually 80%)
You may be billed: What you might owe (usually 20%)
Example
DateServiceAmount ChargedMedicare ApprovedMedicare PaidYou May Be Billed3/15Office visit$200$100$80$20
What this means:
Doctor charged $200
Medicare only approves $100 for this service
Medicare paid $80 (80%)
You owe $20 (20% coinsurance)
Doctor can't charge you the extra $100—they must accept Medicare's approved amount.
Section 2: Deductible Information
Shows:
Part A deductible: $1,632 (per benefit period)
Part B deductible: $257 (annual)
How much you've paid toward it
Once you meet the deductible, Medicare pays its share.
Section 3: Claims Processing Details
Claim number: Reference for the service
Status: Processed, pending, denied
Remarks: Explanations or next steps
Medicare Advantage EOBs
If you have Medicare Advantage, you get EOBs from your insurance company (not Medicare).
Shows:
Services received
Plan's copay amount
What you owe
Progress toward out-of-pocket maximum
Example:
ServiceDateCopayPaid by PlanPrimary care visit3/15$15$85Lab work3/15$0$50Total you owe$15
Simpler than Medicare MSN—you just pay the copay.
Common EOB Terms Explained
Amount Charged: What the provider billed (often inflated)
Allowed Amount: What Medicare/your plan actually pays for this service
Coinsurance: Your share (usually 20% with Original Medicare)
Copay: Fixed amount you pay (Medicare Advantage)
Deductible: Amount you pay before insurance kicks in
Provider Adjustment: The difference the provider writes off (can't charge you)
Claim Status:
Processed: Handled, shows payment
Pending: Still being reviewed
Denied: Not covered, you may owe full amount
What You Actually Owe
With Original Medicare
You owe:
Part B deductible ($257/year) until met
20% coinsurance for most services
Part A deductible if hospitalized
If you have Medicare Supplement: It pays most/all of what you owe
Example with Supplement:
Doctor visit: $100 Medicare-approved
Medicare pays: $80
You owe: $20
Supplement pays: $20
You pay: $0 (after deductible)
With Medicare Advantage
You owe: Just your copay (shown on EOB)
Example:
Specialist visit
Copay: $40
You pay: $40
When the EOB Shows $0 Owed
Preventive services:
Annual Wellness Visit
Mammogram
Colonoscopy
Flu shot
These are FREE if you use in-network providers.
EOB will show:
Service provided
Medicare/plan paid: Full amount
You owe: $0
When You Might Owe More
Service Not Covered
EOB will show:
Denied claim
Reason: "Not covered" or "Not medically necessary"
You may owe: Full amount
What to do: Call provider to discuss or appeal if you think it should be covered.
Out-of-Network Provider (Medicare Advantage)
EOB shows higher cost:
Service provided out-of-network
Plan paid partial amount
You owe: Higher coinsurance
What to do: Use in-network providers for non-emergencies.
Provider Doesn't Accept Assignment (Original Medicare)
Rare, but:
Provider doesn't accept Medicare-approved amount
Can charge up to 15% more
EOB shows "excess charges"
What to do: Use providers who accept assignment (most do).
Checking for Errors
Review Every EOB
Look for:
Services you didn't receive
Wrong dates
Duplicate charges
Services at facilities you didn't visit
Fraud is common—verify everything!
If You Find an Error
Step 1: Compare EOB to your records
Step 2: Call the provider to verify
Step 3: If error confirmed, call Medicare or your plan
Step 4: File an appeal if necessary
Report fraud: 1-800-HHS-TIPS
Understanding the Bill vs EOB
You'll Receive Two Documents
1. EOB (from Medicare or insurance):
Summary of what happened
Shows what's been paid
Not a bill
2. Bill (from provider):
Shows what you owe
Has payment instructions
This is what you pay
Wait for both before paying. Make sure they match!
When Bills Don't Match EOBs
This happens sometimes:
Scenario 1: Provider billed before insurance processed
Solution: Wait for EOB, then compare. Call provider if needed.
Scenario 2: Provider billing more than EOB says you owe
Solution: Call provider's billing dept with your EOB.
Scenario 3: You already paid copay at visit
Solution: EOB may still show amount—but note you paid at time of service.
Organizing Your Medicare Paperwork
Create a system:
Binder with sections:
Insurance cards (copies)
EOBs (file by date)
Bills (mark "paid" when done)
Receipts
Medication records
Keep EOBs for: At least 1 year (3 years is better)
Why: Needed for taxes, disputes, tracking costs.
Accessing EOBs Online
Medicare.gov
Create MyMedicare account:
View all claims
Download EOBs
Check coverage
See deductible progress
Faster than waiting for mail.
Insurance Company Portal
Medicare Advantage or Part D:
Register on plan website
View claims in real-time
Download EOBs
See out-of-pocket tracker
Common Questions
"Do I need to do anything with my EOB?"
Just review it for accuracy. Keep for your records.
"When do I actually pay?"
When you receive a bill from the provider (separate from EOB).
"How long until I get an EOB?"
Usually 30-60 days after service.
"What if my EOB says I owe money but I never got a bill?"
Wait. Bills can take 60-90 days. If you're concerned, call the provider.
"Can I throw away old EOBs?"
Keep for at least 1 year. Needed for tax deductions or disputes.
Red Flags on EOBs
🚩 Services you didn't receive
🚩 Dates you weren't at that location
🚩 Providers you've never seen
🚩 Amounts that seem excessive
🚩 Duplicate charges for same service
If you see these: Call Medicare or your plan immediately.
Getting Help Understanding Your EOB
If you're confused:
📞 Call Medicare: 1-800-MEDICARE
📞 Call your insurance company: Number on back of card
📞 Call the provider: They can explain charges
📞 Call me: (951) 840-1099
I'll help you understand what you're looking at and what you owe.
The Bottom Line
EOB basics:
It's NOT a bill—it's a summary
Shows what Medicare/your plan paid
Shows what you might owe
Review for accuracy
Keep for records
Wait for actual bill before paying
Don't panic when you get an EOB—just review it carefully and make sure everything looks correct.
Matt Wieczorek | Licensed CA Insurance Agent #4335496 | Temecula, CA
Confused by Medicare paperwork? I'm here to help you understand it.
