X12 837 Part 3: Service Lines (Loop 2400)

You go to the emergency room after a fall. A doctor examines you, someone takes an X-ray, and you leave with a cast. On the claim, those are three separate service lines, each with its own procedure code, charge, units and diagnosis pointer. Payers adjudicate at the line level, so this is where most of the money is decided.

This is the final part of the 837 series. It covers loop 2400 for professional, institutional and dental claims, then closes the file with the trailers. Part 1 and Part 2 cover everything above it.

LX: the line number

Each service line starts with LX, followed by its number: LX*1~, LX*2~. LX plus one SV segment are mandatory for every line.

SV1: professional lines (837P)

LX*1~
SV1*HC:99283*250*UN*1*23**1:2~
LX*2~
SV1*HC:73110:26*45*UN*1*23**1~

Element	Meaning
SV101-1	Code qualifier: HC covers both CPT and HCPCS under HIPAA
SV101-2	Procedure code
SV101-3…	Up to four modifiers
SV102	Line charge
SV103	Unit basis: UN units or MJ minutes
SV104	Quantity
SV105	Place of service, if different from the claim’s
SV107	Diagnosis pointers

Modifiers refine a procedure. In line 2, 26 means the provider is billing only the professional component of the X-ray: reading and interpreting it. The facility that took the image would bill the technical component with TC. (Medical coding basics has more on modifiers.)

Diagnosis pointers in SV107 refer, by position, to the diagnoses listed in the claim’s HI segment. The first pointer is the primary diagnosis for this line, and the rest follow in order of importance. In the example, the ER visit points to diagnoses 1 and 2, and the X-ray only to 1. A wrong pointer can get a line denied as not medically necessary, even when the right diagnosis is on the claim.

SV2: institutional lines (837I)

LX*1~
SV2*0450*HC:99284*1200*UN*1~
LX*2~
SV2*0320*HC:73110*2600.39*UN*1**600~

Element	Meaning
SV201	Revenue code: the department or type of charge (0450 emergency room, 0320 diagnostic X-ray, 0120 semi-private room)
SV202	Procedure code composite (same structure as SV101)
SV203	Line charge
SV204	Unit basis: UN units or DA days
SV205	Quantity
SV207	Non-covered charges on this line

Revenue codes are what make institutional claims different: they place each charge in a hospital department, and they’re often paired with CPT or HCPCS codes for a complete picture. In line 2, $600 of the $2,600.39 charge is marked non-covered (SV207), which the patient may have to pay.

SV3: dental lines (837D)

LX*1~
SV3*AD:D2740*1100*11***1*****1~
TOO*JP*3*M:O:D~

Element	Meaning
SV301	AD (American Dental Association) plus the CDT procedure code
SV302	Line charge
SV303	Place of service
SV304	Oral cavity area, when the procedure isn’t for a specific tooth: 00 entire mouth, 01 upper arch, 02 lower arch, 10/20/30/40 for the four quadrants
SV305	Prosthesis status: I initial placement, R replacement
SV306	Number of procedures
SV311	Diagnosis pointers

TOO gives the tooth: TOO01 = JP (Universal National Tooth Designation System), TOO02 the tooth number, and TOO03 the surfaces worked on. Here, a crown (D2740) on tooth 3, covering the mesial, occlusal and distal surfaces.

PWK at line level

Line-level PWK flags documentation that supports a specific line, such as a certificate of medical necessity for oxygen therapy or durable medical equipment. When a certificate is attached, the line usually also needs the therapy begin date (DTP*463).

Line dates

Qualifier	Date	Used on
472	Service date	P, I, D
454	Initial treatment	P
304	Last seen	P
463	Begin therapy	P
471	Prescription	P
452	Appliance placement	D
196 / 198	Treatment start / completion	D

For dental lines using treatment start and completion dates, don’t also send a service date on that line.

Line references and notes

• REF*6R: line item control number, the provider’s ID for this line, unique within the claim. Payers echo it on the 835, which makes posting easier.
• REF*G1: a line-specific prior authorisation number.
• REF*9B / REF*9D: repriced and adjusted repriced line numbers, from a repricer.
• NTE: a free-text note for this line.

HCP: line repricing

As at claim level, repricers return line-level results in HCP: HCP01 method, HCP02 allowed amount, HCP03 savings, HCP13 reject reason. See Claim Repricing.

Line-level providers

Any line can name its own providers, using the same NM1 codes as loop 2310: DN referring, 72 operating, 82 rendering, 77 service facility. That’s useful when lines were performed by different people, for example a dental claim where line 2 was done by a different dentist from lines 1 and 3.

SVD and CAS: what a previous payer did

When another payer has already processed the claim (coordination of benefits), each line can carry that payer’s results:

SVD*OTHER01*120*HC:99283**1~
CAS*CO*45*130~
DTP*573*D8*20251012~

Element	Meaning
SVD01	Other payer’s ID, matching loop 2330B
SVD02	Amount that payer paid for this line
SVD03	Procedure code the payer adjudicated, which can differ from the one billed
SVD04	Revenue code (837I only)
SVD05	Units paid

If there’s an SVD, there’s usually a CAS explaining the adjustment. Here, CO*45 means $130 was a contractual reduction (charge above the fee schedule). DTP*573 is the date that payer adjudicated the line. The dental SVD uses AD instead of HC.

The trailers

Every envelope that was opened gets closed, with counts the receiver checks:

SE*48*0001~
GE*1*1~
IEA*1*000000001~

• SE: SE01 = number of segments from ST to SE, inclusive; SE02 = the ST02 control number.
• GE: GE01 = number of transaction sets in the group; GE02 = the GS06 group control number.
• IEA: IEA01 = number of functional groups; IEA02 = the ISA13 interchange control number.

A count that’s off by one rejects the whole set, which is why generators should compute them, never hard-code them.

Common pitfalls

• Line charges that don’t add up. The sum of line charges must equal CLM02.
• Pointers to diagnoses that aren’t there. SV107 = 3 when the claim has two diagnoses is a hard reject.
• Units vs dosage. Drug and supply codes are priced per unit, so 15 ml of contrast is SV104 = 15.
• Missing REF*6R. It’s optional, but without it matching 835 payments to lines is harder.
• An SVD with no matching 2330B payer. SVD01 has to point at a payer named in the claim.

Conclusion

Loop 2400 holds the lines: LX numbers them, and SV1, SV2 or SV3 carry the procedure, charge, units and diagnosis pointers for professional, institutional and dental claims. Around them sit line dates, references, repricing, line-level providers and, for secondary claims, the previous payer’s SVD and CAS. The trailers close the file with counts.

With all three parts, you can read any 837 file end to end. The payer’s answer comes back on the 835.

Further watching

From the HealthTech Decoded channel:

• Chapter 3: How to master X12 837 (loop 2400)
• Chapter 3: X12 837 service lines (short)

References

• Stedi: X12 837P reference
• X12: Claim Adjustment Reason Codes

Where this fits

Level 3 · Health data exchange › Healthcare EDI (ANSI X12)

• Previous: X12 837 Part 2: The Claim Information Loop (2300)
• Next: X12 835: Claim Payment and Remittance Advice