EDI 270/271 Eligibility Check Explained: Technical Specification & Practice Guide
The ANSI X12 EDI 270/271 transaction set is the HIPAA-mandated standard for real-time electronic health insurance eligibility verification. The EDI 270 inquiry is transmitted by a practice or clearinghouse to request patient benefits, while the EDI 271 response delivers active coverage status, primary/specialist copays, deductible balances, coinsurance percentages, and pre-authorization requirements — typically in under 4 seconds.
Key Technical & Operational Takeaways
- EDI 270 (Health Care Eligibility Benefit Inquiry): Standardized ANSI X12 payload sent by medical practices containing Provider NPI, Patient Name, DOB, Member ID, Group Number, Payer ID, and Service Type Code (STC).
- EDI 271 (Health Care Eligibility Benefit Response): Electronic response payload containing coverage status codes (Code 1 = Active), financial responsibility rules, copays, deductibles, and pre-auth flags.
- Service Type Codes (STC): Code 30 (General Health Benefit Plan), Code 1 (Medical Care), Code 98 (Professional Office Visit), Code 33 (Chiropractic), Code 35 (Dental).
- AAA Rejection Error Codes: Identifies why a payer rejected an inquiry (e.g. AAA03 = 42 "Cannot Identify Subscriber", AAA03 = 72 "Invalid Subscriber ID").
- CAQH CORE & Medicare HETS Rules: Federal standards enforcing sub-20-second real-time response SLAs and standardized benefit structures.
1. What Are EDI 270 and EDI 271 Transactions?
Under the Health Insurance Portability and Accountability Act of 1996 (HIPAA) Administrative Simplification provisions, the U.S. Department of Health and Human Services (HHS) adopted the ANSI X12 Version 5010X279A1 standard as the official format for electronic eligibility transactions.
Instead of staff logging into individual payer portals or waiting 15–20 minutes on hold per patient, an EDI 270/271 real-time query executes programmatically between your practice software, an eligibility clearinghouse, and insurance payers (such as Aetna, Blue Cross Blue Shield, Cigna, UnitedHealthcare, and Medicare HETS).
Sent from your clinic system to the clearinghouse. Contains Provider NPI, Subscriber Member ID, Patient Name, DOB, Payer ID, and Service Type Code (STC).
Returned by the insurance carrier. Transmits active coverage status, copay dollars, deductible remaining balances, out-of-pocket maximum caps, and pre-authorization warning flags.
2. Sample ANSI X12 5010 EDI 270 & 271 Raw Segment Code
To understand how eligibility data is structured under HIPAA X12 5010 rules, examine the raw segment structure below. Each segment is terminated by a tilde (~), and elements within segments are separated by asterisks (*).
ISA*00* *00* *ZZ*CLINICVERIFY *ZZ*PAYERID999 *261024*1430*^*00501*000000001*0*P*:~ GS*HS*CLINICVERIFY*PAYERID999*20261024*1430*1*X*005010X279A1~ ST*270*0001*005010X279A1~ BHT*0022*13*TRANX2026102401*20261024*1430~ HL*1**20*1~ NM1*PR*2*BLUE CROSS BLUE SHIELD*****PI*BCBS01~ HL*2*1*21*1~ NM1*1P*1*SMITH*JOHN***XX*1982736450~ HL*3*2*22*0~ NM1*IL*1*JENKINS*SARAH****MI*BCB98234101~ DMG*D8*19880512*F~ DTP*291*D8*20261024~ EQ*30~ SE*13*0001~ GE*1*1~ IEA*1*000000001~
ISA*00* *00* *ZZ*PAYERID999 *ZZ*CLINICVERIFY *261024*1430*^*00501*000000001*0*P*:~ GS*HB*PAYERID999*CLINICVERIFY*20261024*1430*1*X*005010X279A1~ ST*271*0001*005010X279A1~ BHT*0022*11*TRANX2026102401*20261024*1430~ HL*1**20*1~ NM1*PR*2*BLUE CROSS BLUE SHIELD*****PI*BCBS01~ HL*2*1*21*1~ NM1*1P*1*SMITH*JOHN***XX*1982736450~ HL*3*2*22*0~ NM1*IL*1*JENKINS*SARAH****MI*BCB98234101~ EB*1*IND*30**PPO CHOICE PLUS~ EB*B*IND*98***27*30.00~ EB*C*IND*30***23*450.00~ SE*14*0001~ GE*1*1~ IEA*1*000000001~
Note: EB*1 indicates Active Coverage; EB*B with code 98 and 30.00 specifies a $30.00 Copay for Professional Office Visits; EB*C with 450.00 indicates $450.00 Remaining Deductible.
3. Service Type Codes (STCs) Reference Table
When requesting eligibility, element EQ01 specifies the Service Type Code (STC). Payers evaluate this code to return general vs. specialty benefit details:
| STC Code | Benefit Name | Primary Use Case | Typical Benefit Returned |
|---|---|---|---|
| STC 30 | Health Benefit Plan Coverage | General eligibility check | Active/Inactive status, general deductibles, OOP max |
| STC 1 | Medical Care | Physician & clinical treatment | In-network vs out-of-network coinsurance % |
| STC 98 | Professional (Office) Visit | Primary & specialist check-in | Exact primary copay ($25–$35) & specialist copay ($50–$85) |
| STC 33 | Chiropractic / Specialty | Specialty care practices | Visit limit caps (e.g., 20 visits/yr) & pre-auth alerts |
| STC 35 | Dental Care | Dental clinics | Preventive %, annual max limits, frequency rules |
| STC 88 | Pharmacy / Rx Coverage | Prescription benefit checks | Rx BIN, PCN, Rx Group, Tier copays |
4. AAA Rejection Error Codes & Resolution Matrix
When a payer cannot process an EDI 270 request, an AAA segment is returned inside the EDI 271 response payload. Element AAA03 provides the exact error code. Below are the most common AAA rejection codes and how front-desk staff or billing managers resolve them:
| AAA03 Code | Payer Error Description | Root Cause | Front-Desk Resolution Playbook |
|---|---|---|---|
| AAA03 = 42 | Cannot Identify Subscriber | Member ID typo or incorrect Payer ID selected | Re-scan insurance card using OCR; check for prefix/suffix letters on subscriber card. |
| AAA03 = 72 | Invalid/Missing Subscriber ID | Subscriber ID field blank or malformed formatting | Verify alphanumeric formatting (e.g. BCBS 3-character alpha prefix + 8 numbers). |
| AAA03 = 73 | Ineligible / Terminated Coverage | Policy canceled or subscriber changed employers | Ask patient for new insurance card or secondary coverage; notify biller before check-in. |
| AAA03 = 58 | Invalid Date of Birth | DOB in inquiry does not match payer eligibility record | Check patient driver's license DOB vs. chart record; verify subscriber vs dependent DOB. |
| AAA03 = 15 | Required Field Missing | Provider NPI or Service Date missing from request | Ensure billing NPI is registered in clinic settings and service date is present. |
5. CAQH CORE Rules & Medicare HETS 270/271 Interface
Under federal regulations, clearinghouses and health plans must comply with CAQH CORE (Council for Affordable Quality Healthcare Operating Rules) Phase I, II, and III rules:
CAQH CORE mandates that real-time EDI 270/271 transactions must return responses within 20 seconds or less (ClinicVerify averages under 4 seconds across 900+ clearinghouse connections).
Payers are required to explicitly break down co-payment amounts, remaining deductible balances, and out-of-pocket limits for base health service categories (STC 30, STC 1, STC 98).
For Medicare Part A and Part B beneficiaries, inquiries pass through CMS HETS (HIPAA Eligibility Transaction System) using the beneficiary's MBI (Medicare Beneficiary Identifier) and provider NPI over secure SOAP/REST web services.