837 file anatomy

Structural reference for the 837 claim transaction. Written for humans reading a rejection message and for engineers or agents parsing files.

The loop hierarchy

X12 organizes data into nested loops. The 837P’s key loops:

Loop	Contains
1000A	Submitter
1000B	Receiver
2000A	Billing provider hierarchical level
2010AA	Billing provider, your PC: name, NPI, Tax ID, address
2010AB	Pay-to address, if different
2000B	Subscriber hierarchical level
2010BA	Subscriber, member ID, name, DOB
2010BB	Payer
2000C	Patient hierarchical level (only when the patient is not the subscriber)
2010CA	Patient
2300	Claim, total charge, POS, frequency code, diagnoses, prior auth
2310A	Referring provider
2310B	Rendering provider, the individual clinician
2310C	Service facility location
2310D	Supervising provider
2400	Service line, one per procedure
2410	Drug identification, where applicable
2420A	Line-level rendering provider, where it differs from the claim level

Annotated example

An 837P fragment with each segment explained:

ISA*00*          *00*          *ZZ*SUBMITTERID    *ZZ*PAYERID        *260813*1200*^*00501*000000001*0*P*:~
GS*HC*SUBMITTERID*PAYERID*20260813*1200*1*X*005010X222A1~
ST*837*0001*005010X222A1~
BHT*0019*00*REF123*20260813*1200*CH~
NM1*41*2*MERIDIAN HEALTH PARTNERS*****46*SUBMITTERID~
NM1*40*2*REGIONAL BCBS*****46*PAYERID~
HL*1**20*1~
NM1*85*2*PRIYA SHAH MD PC*****XX*1234567890~
N3*100 MAIN ST~
N4*DENVER*CO*80202~
REF*EI*880000000~
PRV*BI*PXC*207N00000X~
HL*2*1*22*0~
SBR*P*18*******CI~
NM1*IL*1*CHEN*MARGARET****MI*ABC123456789~
DMG*D8*19710415*F~
NM1*PR*2*REGIONAL BCBS*****PI*PAYERID~
CLM*PATACCT001*480.00***11:B:1*Y*A*Y*Y~
REF*G1*AUTH987654~
HI*ABK:L82.1*ABF:D22.5~
NM1*82*1*SHAH*PRIYA****XX*1987654321~
LX*1~
SV1*HC:99213:25*285.00*UN*1***1~
DTP*472*D8*20260801~
LX*2~
SV1*HC:11102*195.00*UN*1***1:2~
DTP*472*D8*20260801~
SE*24*0001~
GE*1*1~
IEA*1*000000001~

Segment by segment

Segment	Meaning
`ISA`	Interchange envelope: sender, receiver, date, control number, delimiters
`GS`	Functional group. `HC` = health care claim. `005010X222A1` identifies the 837P implementation guide
`ST`	Transaction set start
`BHT`	Beginning of hierarchical transaction. `CH` = chargeable
`NM1*41`	Submitter, who transmitted the file
`NM1*40`	Receiver
`HL1201`	Hierarchical level: `20` = information source (billing provider)
`NM1*85`	Billing provider. `2` = organization; `XX` qualifies the NPI. This is your PC.
`N3` / `N4`	Address
`REF*EI`	Employer ID, the Tax ID
`PRVBIPXC*...`	Billing provider taxonomy. `PXC` qualifies a taxonomy code
`HL21220`	`22` = subscriber level
`SBRP18...CI`	Subscriber: `P` = primary, `18` = self, `CI` = commercial insurance
`NM1*IL`	Subscriber. `MI` qualifies the member ID
`DMGD8...`	Demographics: date format `D8` = CCYYMMDD
`NM1*PR`	Payer
`CLM`	Claim: patient account number, total charge, then the composite `11:B:1` where `11` = place of service (office)
`REF*G1`	Prior authorization number
`HIABK:...ABF:...`	Diagnoses. `ABK` = principal ICD-10-CM; `ABF` = additional
`NM1*82`	Rendering provider, the individual clinician’s Type 1 NPI
`LX`	Service line counter
`SV1HC:99213:25285.00UN1***1`	Service line: `HC` qualifies a HCPCS/CPT code, `99213` with modifier `25`, $285.00, `UN` units, 1 unit, diagnosis pointer `1`
`SV1HC:11102...***1:2`	Second line, pointing to diagnoses 1 and 2
`DTP472D8*...`	Service date. `472` = service
`SE` / `GE` / `IEA`	Transaction, group, and interchange trailers with segment counts

The fields that cause most rejections

Field	Location	Failure
Billing provider legal name	`NM1*85`	Doesn’t match the payer’s records / the CP 575
Billing provider NPI	`NM1*85`, `XX` qualifier	Wrong entity’s Type 2 in a multi-PC group
Tax ID	`REF*EI`	Doesn’t match enrollment
Taxonomy	`PRVBIPXC`	Doesn’t match the enrolled taxonomy
Rendering provider NPI	`NM1*82`	Not credentialed or not linked to the group contract
Subscriber ID	`NM1*IL`, `MI` qualifier	Transposed digits; missing alpha prefix
Date of birth	`DMG`	Doesn’t match the payer’s record
Place of service	`CLM05` composite	Wrong code, especially telehealth `02` vs `10`
Prior authorization	`REF*G1`	Obtained but never entered into the structured field
Diagnosis pointers	`SV107` composite	Pointing to a diagnosis that doesn’t support the line
Claim frequency code	`CLM05-3`	`1` original, `7` replacement, `8` void, resubmitting an adjudicated claim as `1` denies as duplicate
Service date	`DTP*472`	Before the rendering provider’s effective date

Six of the top failures trace back to enrollment, not billing. See Set up EDI, ERA, and EFT.

837I, institutional differences

Element	837P	837I
Implementation guide	`005010X222A1`	`005010X223A2`
Paper analogue	CMS-1500	UB-04
Service line codes	CPT/HCPCS	CPT/HCPCS plus revenue codes
Distinctive segments	—	`CL1` (institutional claim code, admission type/source, patient status), revenue codes in `SV2`
Bill type	—	Required, in `CLM05-1`
Admission and discharge data	—	Required for inpatient
Diagnosis types	Principal plus additional	Principal, admitting, external cause, present-on-admission indicators

837D, dental differences

Element	837P	837D
Implementation guide	`005010X222A1`	`005010X224A2`
Paper analogue	CMS-1500	ADA Dental Claim Form
Procedure codes	CPT/HCPCS (`HC` qualifier)	CDT (`AD` qualifier)
Service line segment	`SV1`	`SV3`
Tooth-level data	—	`TOO` segment, tooth number and surfaces
Oral cavity designation	—	Quadrants and arches
Orthodontic data	—	Treatment months, appliance placement

🦷 837D is not “837P with different codes.” The SV3 and TOO segments carry tooth-level detail with no professional-claim equivalent. Confirm your clearinghouse supports 837D before committing. See Dental: the DSO model.

Corrected claims

Frequency code (`CLM05-3`)	Meaning
`1`	Original
`7`	Replacement of a prior claim
`8`	Void / cancel a prior claim

A 7 or 8 must reference the original claim number, typically in REF*F8 (payer claim control number).

Never resubmit an adjudicated claim with frequency code 1. It denies as a duplicate (CARC 18) and may consume your correction window.

CPOM & Legal

Payers

Clearinghouses & Vendors

EDI & Code Sets

Banking & Payments

Glossary & Appendices

The loop hierarchy

Annotated example

Segment by segment

The fields that cause most rejections

837I, institutional differences

837D, dental differences

Corrected claims

​The loop hierarchy

​Annotated example

​Segment by segment

​The fields that cause most rejections

​837I, institutional differences

​837D, dental differences

​Corrected claims

The loop hierarchy

Annotated example

Segment by segment

The fields that cause most rejections

837I, institutional differences

837D, dental differences

Corrected claims