Understanding ERAs and EOBs: Decoding Insurance Payment Information

Overview

Understanding ERAs and EOBs: Decoding Insurance Payment Information

When insurance payments arrive at your practice, they come with detailed information explaining what was paid, what wasn't, and why. This information arrives as either an ERA (Electronic Remittance Advice) or an EOB (Explanation of Benefits)—and understanding how to read these documents is essential for accurate payment posting, denial management, and revenue cycle health.

Key takeaways

• Understanding ERAs and EOBs: Decoding Insurance Payment Information When insurance payments arrive at your practice, they come with detailed information explaining what was paid, what wasn't, and why.
• This information arrives as either an ERA (Electronic Remittance Advice) or an EOB (Explanation of Benefits)—and understanding how to read these documents is essential for accurate payment posting, denial management, and revenue cycle health.
• Yet for many practices, ERAs and EOBs might as well be written in a foreign language.
• This guide decodes these documents so you can understand exactly what payers are telling you—and take appropriate action.

Details

Yet for many practices, ERAs and EOBs might as well be written in a foreign language. This guide decodes these documents so you can understand exactly what payers are telling you—and take appropriate action.

ERA vs. EOB: What's the Difference?

Electronic Remittance Advice (ERA / 835)

What it is: An electronic file that contains payment information in standardized format (ANSI X12 835 transaction).

How you receive it: Electronically through your clearinghouse or directly from payers via a secure portal.

Benefits:

• Automated payment posting possible
• Standardized format across payers
• Faster processing
• Fewer manual errors
• Searchable and sortable data

What it contains:

• Payment amounts
• Adjustment codes and reasons
• Patient responsibility amounts
• Service line details
• Remittance advice codes

Explanation of Benefits (EOB)

What it is: A paper or PDF document explaining payment decisions—essentially a human-readable version of the same information.

How you receive it: Mailed to provider and/or patient; sometimes available via payer portal.

Differences from ERA:

• Not standardized across payers (each looks different)
• Cannot be automatically imported to billing systems
• Requires manual posting
• More time-consuming to process

The industry trend: ERAs are becoming standard. Most practices should enroll in ERA delivery from all major payers to improve efficiency.

The Anatomy of an ERA (835 File)

Header Information

The beginning of an ERA contains:

Check/EFT information:

• Payment amount
• Payment method (check number or EFT trace number)
• Payment date
• Payer name and ID

Payee information:

• Your practice name
• NPI and Tax ID
• Address

Claim-Level Information

For each claim included in the remittance:

Patient and claim identification:

• Patient name
• Member ID
• Claim number
• Date(s) of service
• Claim status (paid, denied, adjusted)

Payment summary:

• Billed amount
• Allowed amount
• Paid amount
• Adjustment amounts
• Patient responsibility

Service Line Detail

For each service on the claim:

Field	Description	Example
CPT/HCPCS Code	Service billed	90834
Modifier	Any modifiers	95 (telehealth)
Units	Quantity billed	1
Billed Amount	What you charged	$150.00
Allowed Amount	Payer's allowed rate	$102.00
Paid Amount	What payer paid	$81.60
Adjustment Amount	Difference explained	$48.00 (contractual)
Patient Responsibility	Copay/deductible/coinsurance	$20.40

Adjustment Codes

This is where the critical information lives. Adjustment codes explain why the paid amount differs from the billed amount.

Understanding Adjustment Codes

The Code Structure

ERA adjustments use a combination of:

Claim Adjustment Group Codes: Why the adjustment was made Claim Adjustment Reason Codes (CARCs): Specific reason for adjustment Remittance Advice Remark Codes (RARCs): Additional information

Claim Adjustment Group Codes

Code	Meaning	Action
CO	Contractual Obligation	Write off—this is your contracted discount
PR	Patient Responsibility	Bill patient for this amount
OA	Other Adjustment	Review CARC for specifics
CR	Correction/Reversal	Previous payment being adjusted
PI	Payer Initiated Reduction	Payer reducing payment; may be appealable

Common Claim Adjustment Reason Codes (CARCs)

Contractual adjustments (CO group—typically write off):

CARC	Description	Meaning
45	Charge exceeds fee schedule/maximum allowable	Your charge exceeds contracted rate—normal
97	The benefit for this service is included in another service	Bundling; one code includes another
253	Sequestration	Medicare reduction (currently ~2%)

Patient responsibility (PR group—bill patient):

CARC	Description	Meaning
1	Deductible	Patient's deductible applies
2	Coinsurance	Patient's coinsurance applies
3	Copay	Patient's copay applies

Claim issues (may be correctable):

CARC	Description	Action
4	Procedure code inconsistent with modifier	Review modifier usage
5	Procedure code inconsistent with place of service	Check POS code
16	Claim lacks information	Review what's missing
18	Exact duplicate claim	Claim already processed
22	Coordination of benefits	Other insurance primary
27	Expenses incurred after coverage terminated	Verify coverage dates
29	Time limit for filing expired	Timely filing issue
31	Patient cannot be identified	Member ID/DOB issue
32	Our records indicate this was not pre-certified	Prior auth required
35	Lifetime benefit maximum reached	Out of benefits
50	Non-covered service	Service not covered
96	Non-covered charge	Charge not covered
109	Claim not covered by this payer	Wrong payer billed
197	Precertification/auth was not obtained	Prior auth missing

Coding and medical necessity issues:

CARC	Description	Action
11	Diagnosis inconsistent with procedure	Review DX-CPT match
56	Procedure not appropriate for diagnosis	Medical necessity
146	Diagnosis code missing or invalid	Add/correct diagnosis
151	Payment adjusted based on review	May need appeal
181	Procedure code was invalid on DOS	Check code validity
182	Procedure modifier invalid	Check modifier

For comprehensive denial management, see our claim denials guide.

Remittance Advice Remark Codes (RARCs)

RARCs provide additional context. Common examples:

RARC	Description
M1	X-ray not taken within required timeframe
M15	Services may be denied if not appealed within...
N30	Patient ineligible on date of service
N95	This payer does not cover this service
N362	Missing/incomplete/invalid prescribing provider
N479	Missing/invalid NDC

Where to look up codes: The Washington Publishing Company maintains the official CARC and RARC code lists.

Reading an EOB

While EOBs vary by payer, most contain similar information presented visually.

Typical EOB Sections

1. Header

• Payer logo and contact info
• Payment date
• Check/EFT number
• Provider information

2. Patient Information

• Patient name
• Member ID
• Claim number

3. Service Details (often in table format)

Column	What It Shows
Date of Service	When service was provided
Procedure	CPT code or description
Billed	What you charged
Allowed	Payer's allowed amount
Deductible	Applied to patient deductible
Copay/Coinsurance	Patient's cost share
Paid	Amount payer pays you
Reason	Why billed and paid differ

4. Totals

• Total billed
• Total allowed
• Total paid
• Total patient responsibility

5. Messages/Remarks

• Explanation of adjustments
• Appeal instructions
• Additional information

Sample EOB Interpretation

Scenario: You billed $150 for 90834 (38-52 minute psychotherapy)

Billed	Allowed	Deductible	Coinsurance	Paid	Reason Code
$150.00	$102.00	$0.00	$20.40	$81.60	45, 2

Interpretation:

• Billed $150: Your charge
• Allowed $102: Payer's contracted/allowable rate
• $48 adjustment (CARC 45): Contractual write-off (CO group)
• 20% coinsurance (CARC 2): Patient owes $20.40 (PR group)
• Paid $81.60: Payer pays 80% of allowed amount
• Action: Write off $48.00; bill patient $20.40; post $81.60 payment

Payment Posting Best Practices

The Posting Workflow

Step 1: Receive ERA/EOB

• Download ERAs from clearinghouse
• Organize paper EOBs by deposit date

Step 2: Match to deposit

• Verify ERA payment amount matches actual deposit
• Investigate discrepancies before posting

Step 3: Post payments

• Apply payment to correct patient and date of service
• Post adjustment codes correctly
• Transfer patient responsibility to patient account

Step 4: Work exceptions

• Review denials and partial payments
• Determine if appeal or correction needed
• Take action within timely filing limits

Step 5: Reconcile

• Ensure all payments posted
• Balance to bank deposit
• Review outstanding items

Common Posting Mistakes

Mistake 1: Posting to wrong patient or date

• Always verify patient name, member ID, and DOS before posting
• Match claim number when possible

Mistake 2: Writing off patient responsibility

• CO adjustments = write off
• PR adjustments = bill patient
• Never write off patient responsibility on insurance-billed claims

Mistake 3: Missing denial follow-up

• Post the denial but also create follow-up task
• Track denial reason to address root cause

Mistake 4: Not reconciling to deposit

• ERA total should match bank deposit
• Investigate any discrepancy

Mistake 5: Ignoring takeback/recoupment

• CR adjustments mean money is being taken back
• Understand why and whether to appeal

Automating Payment Posting

Modern practice management systems can:

• Import 835 files automatically
• Post payments based on ERA data
• Flag exceptions for manual review
• Generate patient statements from PR amounts
• Track denial reasons for reporting

Benefits of automation:

• Faster posting (minutes vs. hours)
• Fewer errors
• Staff focus on exceptions, not routine posting
• Better denial tracking

Denial Management from ERAs

Identifying Denials

Denials appear in ERAs as:

• $0.00 paid amount with adjustment codes
• Specific denial CARCs (4, 5, 16, 18, etc.)
• Claim status codes indicating rejection

Categorizing Denials

Category	Examples	Action
Correctable	Missing info, wrong modifier, invalid code	Correct and resubmit
Appealable	Medical necessity, auth issues	File appeal
Write-off	Non-covered, timely filing	Write off (may need patient notice)
Other payer	COB, wrong payer	Bill correct payer

Denial Tracking

Track denials to identify patterns:

By reason code: What's causing most denials? By payer: Which payers deny most? By service: Which services get denied? By provider: Are certain providers having issues?

Use this data to:

• Fix systemic issues
• Train staff on problem areas
• Negotiate with problematic payers
• Improve front-end processes

For detailed denial management strategies, see our claim denials guide.

Understanding Specific Payment Scenarios

Partial Payment

What it looks like: Paid amount is less than expected, but not zero

Common causes:

• Deductible applied (patient responsibility)
• Coinsurance/copay applied (patient responsibility)
• Bundling reduced payment (may need appeal)
• Fee schedule lower than billed (contractual)
• Sequestration (Medicare reduction)

Action: Review adjustment codes to understand why

Claim Paid at Zero

What it looks like: $0.00 paid; entire amount adjusted

This is a denial. Review CARC codes:

• Is it correctable? Resubmit with correction
• Is it appealable? File appeal
• Is it legitimate? Write off

Negative Remittance / Recoupment

What it looks like: Negative payment amount; CR group code

What it means: Payer is taking back previously paid money

Common reasons:

• Duplicate payment recovery
• Audit findings
• Coordination of benefits adjustment
• Patient eligibility reversal

Action:

• Understand why takeback is occurring
• Determine if you should appeal
• May need to collect from patient if eligibility issue
• Track takebacks for financial planning

Overpayment

What it looks like: Paid amount exceeds expected

What to do:

• Verify it's actually an overpayment
• Don't spend it—payer will likely recoup
• Consider proactively refunding
• Document carefully

Multiple Claims on One ERA

Large ERAs may contain many claims. Your system should:

• Import all claims from the file
• Match each to the correct patient/date
• Handle each payment appropriately
• Flag any that don't match existing claims

Special Situations

Secondary Payer Payments

When you bill a secondary payer:

What you send: Claim + primary payer EOB/ERA What you receive: Secondary ERA showing coordination

Key elements:

• What primary paid
• What secondary considers remaining patient responsibility
• What secondary pays
• What patient owes (should be minimal if both paid correctly)

Out-of-Network Payments

Out-of-network claims often show:

• Lower allowed amounts
• Higher patient responsibility percentages
• Balance billing considerations

What you can collect from patient depends on:

• State balance billing laws
• Payer contract terms
• Your patient financial agreements

Medicare Secondary Payer

When Medicare is secondary:

• Bill primary first
• Bill Medicare with primary payment info
• Medicare pays based on remaining allowed amount
• Payment calculations are complex—review carefully

For more on Medicare billing, see our Medicare billing guide.

ERA/EOB Troubleshooting

"I can't find the claim"

Possible causes:

• ERA for different provider/TIN
• Claim number doesn't match your records
• Claim crossed to different date range
• Claim was adjusted from previous payment

"Payment doesn't match deposit"

Check for:

• Multiple ERAs included in one deposit
• Recoupments reducing total
• Prior overpayment being deducted
• Payment to wrong account

"I don't understand the adjustment"

Steps:

1. Look up CARC and RARC codes
2. Review claim to see what might have triggered
3. Call payer if still unclear
4. Document the explanation for future reference

"Patient responsibility seems wrong"

Verify:

• Deductible status at time of service
• Coinsurance percentage in contract
• Whether out-of-pocket maximum was reached
• Coordination of benefits situation

Technology and ERAs

ERA Enrollment

To receive ERAs, you must enroll with each payer:

• Through clearinghouse (they handle enrollment)
• Direct with payer (payer portal setup)
• Via enrollment forms submitted to payer

Enrollment typically requires:

• Provider NPI and Tax ID
• Clearinghouse ID or direct connection info
• Payment delivery preferences
• Authorized contacts

ERA Management in Your Practice Management System

Your system should:

• Receive and import 835 files
• Match payments to claims
• Post automatically with exception flagging
• Display ERA data in readable format
• Store original 835 for reference
• Generate reports on payment trends

Clearinghouse Features

Good clearinghouses provide:

• ERA aggregation from multiple payers
• File conversion and normalization
• Reporting on payment patterns
• Denial analytics
• Integration with your PM system

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Frequently Asked Questions

What's the difference between allowed amount and paid amount?

Allowed amount: The maximum the payer will pay/recognize for a service (your contracted rate). Paid amount: What the payer actually pays you after applying deductible, coinsurance, and copay. Paid amount = Allowed amount - Patient responsibility.

Should I always write off CO (Contractual Obligation) adjustments?

Generally yes—CO adjustments represent your contracted discount with the payer. You agreed to accept less than billed charges. However, review the specific CARC code; some CO adjustments may warrant review.

Can I bill the patient for amounts adjusted under CO?

No. Contractual adjustments (CO) are your write-off. You cannot balance bill the patient for amounts you've contractually agreed to accept as full payment.

How do I know if something is a denial vs. just an adjustment?

A denial results in $0 payment with reason codes indicating why the claim wasn't paid (missing info, not covered, auth issues). An adjustment is a modification to what you billed (fee schedule reduction, bundling) that still results in payment.

What should I do with CARCs I don't recognize?

Look them up in the official CARC list at WPC-EDI. If still unclear after reading the definition, call the payer for clarification. Document what you learn for future reference.

How long should I keep ERA/EOB records?

Keep ERA/EOB records for at least 7-10 years. They're essential documentation for audits, appeals, and financial records. Most states require retention for minimum of 7 years. Check your state's specific requirements.

My ERA shows a recoupment I don't understand. What do I do?

Contact the payer immediately. Request explanation in writing. Determine if the recoupment is valid. If you disagree, file an appeal. Track the recoupment and its resolution.

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Want to simplify payment posting and denial management? Ease Health's platform includes automated ERA processing, intelligent payment posting, and denial tracking to help you maximize collections. Schedule a demo to see how we can help.

Related Glossary Terms

• ERA — Electronic Remittance Advice format and auto-posting
• EOB — Explanation of Benefits and how it differs from ERAs
• Revenue Cycle Management — How payment posting fits in the full revenue cycle
• Claim Denial — Understanding denial codes found in ERAs
• CPT Codes — The procedure codes referenced in ERA line items

Next steps

• Review the key takeaways and adapt them to your practice workflow.
• Use the details section as a checklist when you implement or troubleshoot.
• Share this with your billing or admin team to align on process and terminology.