# CARC 2 Denial Code (Coinsurance Amount) | ANSI 835 EDI Spec
> Comprehensive healthcare EDI technical reference and denial resolution guide for Claim Adjustment Reason Code 2 (Coinsurance Amount) under ANSI ASC X12 835 005010X221A1.

- **Canonical URL:** https://stanzaapi.com/tools/x12-parser/carc/carc-2-coinsurance-amount
- **Governing Standard:** ANSI ASC X12 Standards (005010) (Accredited Standards Committee X12 / HIPAA 5010)
- **Edge Latency SLA:** <2ms Edge (Cloudflare V8 Isolates)
- **Execution Model:** Pure compute $f(x) = y$, 100% In-Memory (Zero Store, Zero Log)

## Technical Overview & Governing Rules
Claim Adjustment Reason Code (CARC) 2 communicates: "Coinsurance Amount.".

In ANSI X12 835 Electronic Remittance Advice (ERA) files, CARC 2 is reported in Loop 2110 (Service Payment Information) or Loop 2100 (Claim Payment Information) under the Claim Adjustment (CAS) segment with Group Code 'PR' (Patient Responsibility), formatted as: CAS*PR*2*AMOUNT~.

Root Cause: Standard cost-sharing percentage split (e.g., 80/20 plan) where patient is responsible for their designated percentage of allowed charges.

Adjudication & Appeal Strategy: Post payer payment and route remaining coinsurance balance to patient billing or secondary/supplemental insurance.

## Specification Matrix
| Attribute | Value | Technical Guidance |
| --- | --- | --- |
| Reason Code | CARC 2 | Coinsurance Amount |
| Standard Group Code | PR | Patient Responsibility |
| ANSI 835 Segment | CAS*PR*2*AMOUNT~ | Loop 2110 or Loop 2100 |
| Balance Billing Patient | Allowed up to the patient percentage defined in adjudication. | Compliance with billing regulations |
| Common RARCs | MA01 | Remittance Advice Remark Codes |
| Recommended Action | Post payer payment and route remaining coinsurance balance to patient billing or secondary/supplemental insurance. | Workflow for billing teams |

## Standard JSON Response Model
```json
{
  "transactionType": "835",
  "claimNumber": "CLM-2026-001",
  "adjudication": {
    "billedAmount": 500,
    "paidAmount": 0,
    "adjustments": [
      {
        "groupCode": "PR",
        "groupName": "Patient Responsibility",
        "reasonCode": "2",
        "reasonDescription": "Coinsurance Amount",
        "adjustmentAmount": 500
      }
    ]
  }
}
```

## Frequently Asked Questions & Edge Cases
### Q: What does CARC 2 mean on an 835 ERA?
**A:** CARC 2 signifies: "Coinsurance Amount.". It explains why the payer did not pay the full billed charge.

### Q: Can a provider balance-bill the patient for CARC 2?
**A:** Allowed up to the patient percentage defined in adjudication.

### Q: How do medical billing teams resolve and appeal CARC 2?
**A:** Post payer payment and route remaining coinsurance balance to patient billing or secondary/supplemental insurance.