Latency: <2ms Edge Availability: 99.99% Standard: ANSI 835 / WPC CARC Verified: Sep 2026 V8 Pure Compute

CARC 31 Denial Code (Patient Cannot Be Identified as Insured) | ANSI 835 EDI Spec

Q: What does CARC 31 mean on an 835 ERA?

CARC 31 signifies: "Patient cannot be identified as our insured.". It explains why the payer did not pay the full billed charge.

Q: Can a provider balance-bill the patient for CARC 31?

Prohibited until insurance eligibility is verified.

Q: How do medical billing teams resolve and appeal CARC 31?

Contact patient to verify current insurance card and Payer ID. Re-route 837 claim to correct clearinghouse Payer ID.

Comprehensive healthcare EDI technical reference and denial resolution guide for Claim Adjustment Reason Code 31 (Patient Cannot Be Identified as Insured) under ANSI ASC X12 835 005010X221A1.

View Pricing & SLA → ⚡ Test in Live Workbench ← Back to Healthcare EDI ANSI X12 Parser API

Official Regulatory Standard & Verification Protocol Authority: Accredited Standards Committee X12 / HIPAA 5010 ↗

Direct Answer Capsule: Comprehensive healthcare EDI technical reference and denial resolution guide for Claim Adjustment Reason Code 31 (Patient Cannot Be Identified as Insured) under ANSI ASC X12 835 005010X221A1. Conforms strictly to ANSI ASC X12 Standards (005010) with zero cold-starts and deterministic edge verification.

Execution SLA

<2ms Edge (Cloudflare V8)

Governing Norm

ANSI 835 / WPC CARC

Active Standard

Sep 2026 Edition

Throughput Limit

512 KB / Payload

Data Privacy

100% In-Memory (Zero Store)

Interactive Edge Workbench

⚡ Live CARC 31 Denial Code (Patient Cannot Be Identified as Insured) | ANSI 835 EDI Spec Interactive Workbench

Test real-time validation and deterministic schema parsing for CARC 31 Denial Code (Patient Cannot Be Identified as Insured) | ANSI 835 EDI Spec directly in your browser. Sub-5ms Cloudflare edge execution with zero setup.

32KB Demo Cap 60 req/min Burst <2ms V8 Compute Zero Data Retention

input.x12 0 B

output.json demo-ready

Status: Ready

{
  "status": "Click 'Run Edge Parse' to test live on Global Edge Isolates..."
}

Specification & Structural Breakdown

Technical Rule Summary: Implementation conforms strictly to ANSI ASC X12 Standards (005010). Data ingestion is fully deterministic: identical inputs always produce bit-for-bit identical outputs without ambient side-effects.

Claim Adjustment Reason Code (CARC) 31 communicates: "Patient cannot be identified as our insured.".

In ANSI X12 835 Electronic Remittance Advice (ERA) files, CARC 31 is reported in Loop 2110 (Service Payment Information) or Loop 2100 (Claim Payment Information) under the Claim Adjustment (CAS) segment with Group Code 'CO' (Contractual Obligation), formatted as: CAS*CO*31*AMOUNT~.

Root Cause: Subscriber ID number does not exist in payer database (often wrong payer ID or switched health plan).

Adjudication & Appeal Strategy: Contact patient to verify current insurance card and Payer ID. Re-route 837 claim to correct clearinghouse Payer ID.

Attribute	Value	Technical Guidance
Reason Code	CARC 31	Patient Cannot Be Identified as Insured
Standard Group Code	CO	Contractual Obligation
ANSI 835 Segment	CASCO31*AMOUNT~	Loop 2110 or Loop 2100
Balance Billing Patient	Prohibited until insurance eligibility is verified.	Compliance with billing regulations
Common RARCs	MA61, N30	Remittance Advice Remark Codes
Recommended Action	Contact patient to verify current insurance card and Payer ID. Re-route 837 claim to correct clearinghouse Payer ID.	Workflow for billing teams

Parsed JSON Response Model

The edge microservice transforms input payloads into strongly-typed hierarchical JSON envelopes with sub-5ms latency:

HTTP 200 JSON Response Envelope

{
  "transactionType": "835",
  "claimNumber": "CLM-2026-001",
  "adjudication": {
    "billedAmount": 500,
    "paidAmount": 0,
    "adjustments": [
      {
        "groupCode": "CO",
        "groupName": "Contractual Obligation",
        "reasonCode": "31",
        "reasonDescription": "Patient Cannot Be Identified as Insured",
        "adjustmentAmount": 500
      }
    ]
  }
}

Copy-Paste Integration Code (5 Languages)

Integrate CARC 31 Denial Code (Patient Cannot Be Identified as Insured) | ANSI 835 EDI Spec directly into your production application with native, zero-dependency code snippets in cURL, Node.js, Python, Go, and C#:

curl --request POST \
  --url "https://healthcare-edi-ansi-x12-parser-837p-835-271.stanzaapi.com/api/v1/x12/parse" \
  --header "Content-Type: application/json" \
  --header "x-api-key: YOUR_API_KEY" \
  --data '{
  "raw": "ISA*00*          *00*          *ZZ*SUBMITTER1     *ZZ*RECEIVER01     *260830*1200*^*00501*000000001*0*P*:~GS*HC*SENDER*RECEIVER*20260830*1200*1*X*005010X222A1~ST*837*0001*005010X222A1~BHT*0019*00*CLAIM001*20260830*1200*CH~NM1*41*2*DR DOE CLINIC*****46*1234567890~PER*IC*SUPPORT*TE*8005551212~HL*1**20*1~NM1*85*2*DR DOE CLINIC*****XX*1992837465~HL*2*1*22*0~NM1*IL*1*SMITH*JANE****MI*W123456780~CLM*CLM001*150.00***11::1*Y*A*Y*Y~LX*1~SV1*HC:99213*150.00*UN*1***1~SE*11*0001~GE*1*1~IEA*1*000000001~"
}'

const response = await fetch("https://healthcare-edi-ansi-x12-parser-837p-835-271.stanzaapi.com/api/v1/x12/parse", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "x-api-key": process.env.API_KEY || "YOUR_API_KEY"
  },
  body: JSON.stringify({
  "raw": "ISA*00*          *00*          *ZZ*SUBMITTER1     *ZZ*RECEIVER01     *260830*1200*^*00501*000000001*0*P*:~GS*HC*SENDER*RECEIVER*20260830*1200*1*X*005010X222A1~ST*837*0001*005010X222A1~BHT*0019*00*CLAIM001*20260830*1200*CH~NM1*41*2*DR DOE CLINIC*****46*1234567890~PER*IC*SUPPORT*TE*8005551212~HL*1**20*1~NM1*85*2*DR DOE CLINIC*****XX*1992837465~HL*2*1*22*0~NM1*IL*1*SMITH*JANE****MI*W123456780~CLM*CLM001*150.00***11::1*Y*A*Y*Y~LX*1~SV1*HC:99213*150.00*UN*1***1~SE*11*0001~GE*1*1~IEA*1*000000001~"
})
});

const data = await response.json();
console.log(data);

import requests
import json

url = "https://healthcare-edi-ansi-x12-parser-837p-835-271.stanzaapi.com/api/v1/x12/parse"
headers = {
    "Content-Type": "application/json",
    "x-api-key": "YOUR_API_KEY"
}
payload = {
    "raw": "ISA*00*          *00*          *ZZ*SUBMITTER1     *ZZ*RECEIVER01     *260830*1200*^*00501*000000001*0*P*:~GS*HC*SENDER*RECEIVER*20260830*1200*1*X*005010X222A1~ST*837*0001*005010X222A1~BHT*0019*00*CLAIM001*20260830*1200*CH~NM1*41*2*DR DOE CLINIC*****46*1234567890~PER*IC*SUPPORT*TE*8005551212~HL*1**20*1~NM1*85*2*DR DOE CLINIC*****XX*1992837465~HL*2*1*22*0~NM1*IL*1*SMITH*JANE****MI*W123456780~CLM*CLM001*150.00***11::1*Y*A*Y*Y~LX*1~SV1*HC:99213*150.00*UN*1***1~SE*11*0001~GE*1*1~IEA*1*000000001~"
}

response = requests.post(url, json=payload, headers=headers)
print(response.json())

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	url := "https://healthcare-edi-ansi-x12-parser-837p-835-271.stanzaapi.com/api/v1/x12/parse"
	payload := []byte(`{"raw":"ISA*00*          *00*          *ZZ*SUBMITTER1     *ZZ*RECEIVER01     *260830*1200*^*00501*000000001*0*P*:~GS*HC*SENDER*RECEIVER*20260830*1200*1*X*005010X222A1~ST*837*0001*005010X222A1~BHT*0019*00*CLAIM001*20260830*1200*CH~NM1*41*2*DR DOE CLINIC*****46*1234567890~PER*IC*SUPPORT*TE*8005551212~HL*1**20*1~NM1*85*2*DR DOE CLINIC*****XX*1992837465~HL*2*1*22*0~NM1*IL*1*SMITH*JANE****MI*W123456780~CLM*CLM001*150.00***11::1*Y*A*Y*Y~LX*1~SV1*HC:99213*150.00*UN*1***1~SE*11*0001~GE*1*1~IEA*1*000000001~"}`)

	req, _ := http.NewRequest("POST", url, bytes.NewBuffer(payload))
	req.Header.Add("Content-Type", "application/json")
	req.Header.Add("x-api-key", os.Getenv("API_KEY"))

	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)
	fmt.Println(string(body))
}

using System;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        using var client = new HttpClient();
        client.DefaultRequestHeaders.Add("x-api-key", Environment.GetEnvironmentVariable("API_KEY") ?? "YOUR_API_KEY");

        var json = @"{""raw"":""ISA*00*          *00*          *ZZ*SUBMITTER1     *ZZ*RECEIVER01     *260830*1200*^*00501*000000001*0*P*:~GS*HC*SENDER*RECEIVER*20260830*1200*1*X*005010X222A1~ST*837*0001*005010X222A1~BHT*0019*00*CLAIM001*20260830*1200*CH~NM1*41*2*DR DOE CLINIC*****46*1234567890~PER*IC*SUPPORT*TE*8005551212~HL*1**20*1~NM1*85*2*DR DOE CLINIC*****XX*1992837465~HL*2*1*22*0~NM1*IL*1*SMITH*JANE****MI*W123456780~CLM*CLM001*150.00***11::1*Y*A*Y*Y~LX*1~SV1*HC:99213*150.00*UN*1***1~SE*11*0001~GE*1*1~IEA*1*000000001~""}";
        var payload = new StringContent(json, Encoding.UTF8, "application/json");

        var response = await client.PostAsync("https://healthcare-edi-ansi-x12-parser-837p-835-271.stanzaapi.com/api/v1/x12/parse", payload);
        var content = await response.Content.ReadAsStringAsync();
        Console.WriteLine(content);
    }
}

Frequently Asked Questions & Technical Notes

What does CARC 31 mean on an 835 ERA?

CARC 31 signifies: "Patient cannot be identified as our insured.". It explains why the payer did not pay the full billed charge.

Can a provider balance-bill the patient for CARC 31?

Prohibited until insurance eligibility is verified.

How do medical billing teams resolve and appeal CARC 31?

Contact patient to verify current insurance card and Payer ID. Re-route 837 claim to correct clearinghouse Payer ID.

Related Healthcare EDI ANSI X12 Parser API Formats

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CARC 31 Denial Code (Patient Cannot Be Identified as Insured) | ANSI 835 EDI Spec

⚡ Live CARC 31 Denial Code (Patient Cannot Be Identified as Insured) | ANSI 835 EDI Spec Interactive Workbench

Specification & Structural Breakdown

Parsed JSON Response Model

Copy-Paste Integration Code (5 Languages)

Frequently Asked Questions & Technical Notes

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