What is an EDI segment?

An EDI segment is a line of data in an EDI file that groups related elements together. Each segment starts with a three-letter tag such as ISA, GS, ST, CLP, or NM1 and is followed by one or more elements separated by delimiters. Segments are the building blocks of X12 EDI transactions like 835 and 837.

Which EDI segments are most important in healthcare transactions?

In healthcare EDI, key segments include ISA and GS for envelope information, ST and SE for transaction headers and trailers, BPR and TRN for payment details, CLP and SVC for claim and service-line information, CAS for adjustments, NM1 for names and identifiers, and DTM for dates. These segments appear frequently in 835 and 837 files.

What does the NM1 segment represent?

The NM1 segment carries name and identifier information for different entities, such as payers, providers, patients, and subscribers. The first element identifies the entity type, such as PR for payer, IL for insured or subscriber, QC for patient, or 82 and 85 for rendering and billing providers. Subsequent elements hold names, ID qualifiers, and ID values.

What is the CLP segment used for in an 835?

In an EDI 835 remittance file, the CLP segment describes claim-level payment information. It typically contains the patient control number, claim status, total charge amount, payment amount, patient responsibility, payer control number, and other claim-level attributes that explain how the claim was adjudicated.

What is the SVC segment used for in an 835?

The SVC segment in an EDI 835 file describes service-line payment information. It includes the procedure or revenue code, line charge amount, line paid amount, units, and sometimes additional identifiers. SVC segments let you see how each individual service on a claim was processed and paid.

How can an EDI segment cheat sheet help analysts and developers?

An EDI segment cheat sheet provides quick reminders of what each segment tag means, where it appears in the transaction, and which elements are most important. This makes it easier for analysts and developers to read raw EDI files, debug mapping issues, and design conversion or ETL logic without constantly referring to long implementation guides.

EDI Segment Cheat Sheet: Common Healthcare X12 Segments

Table of Contents

Envelope Segments (ISA/GS/ST/SE/GE/IEA)
Claim Payment Segments (835)
Claim Submission Segments (837)
Common Segments Across All Transactions
Full Segment Reference Table

Envelope Segments (Used in Every EDI File)

Segment	Meaning	Example
ISA	Interchange header – file-level envelope	`ISA00 00 ZZSENDERIDZZRECEIVERID*...`
GS	Functional group header	`GSHPSENDERRECEIVER2025013112341X005010X221A1`
ST	Transaction set header (identifies 835, 837, etc.)	`ST8350001`
SE	Transaction set trailer	`SE450001`
GE	Functional group trailer	`GE11`
IEA	Interchange trailer – closes the ISA envelope	`IEA1000000001`

Claim Payment Segments (835 ERA Files)

Segment	Purpose	Explanation
BPR	Payment information	Total payment amount, method (ACH, CHK), payment date.
TRN	Trace number	EFT/check trace ID used for bank reconciliation.
N1	Payer/payee info	Payer (PR) and Payee (PE) names/IDs.
CLP	Claim payment details	Claim ID, status, charge amount, paid amount, patient responsibility.
CAS	Adjustments	CO, PR, OA, PI adjustments with reason codes.
SVC	Service line	CPT/HCPCS, billed amount, allowed/paid amounts.
PLB	Provider-level adjustments	Offsets, recoupments, interest.

Claim Submission Segments (837 Files)

Segment	Purpose	Explanation
NM1	Name segment	Patient, subscriber, provider, payer identifiers.
HI	Diagnosis codes	ICD-10 codes for the claim.
SV1	Professional service line	CPT/HCPCS, charges, units.
SV2	Institutional service line	Revenue code, charges, units.
DTM	Date segment	Service dates, admission/discharge dates.
REF	Reference IDs	Authorization numbers, claim numbers, internal tracking IDs.

Common Segments Across All Transactions

Segment	Purpose
N3	Address line 1
N4	City, state, ZIP
PER	Contact information
AMT	Amounts (e.g., allowed amount)
QTY	Quantities (units, visits)

Full Segment Reference Table

This table contains the most frequently used healthcare X12 segments.

Segment	Description
ISA	Interchange Control Header
IEA	Interchange Control Trailer
GS	Functional Group Header
GE	Functional Group Trailer
ST	Transaction Set Header
SE	Transaction Set Trailer
BPR	Financial Information
TRN	Reassociation Trace Number
CLP	Claim Payment Information
CAS	Claim Adjustment
SVC	Service Payment Information
NM1	Individual or Organization Name
HI	Health Information (Diagnosis)
REF	Reference Identifications
DTM	Date/Time References
PLB	Provider-Level Balance

Want to explore these segments in your own EDI file?

Use the in-browser viewer to inspect ISA loops, CLP segments, SVC lines, and more — all without uploading PHI.

Open the EDI Viewer

Compare all EDI tools for viewing, parsing, conversion, or validation.