> ## Documentation Index
> Fetch the complete documentation index at: https://mso.getlemma.com/llms.txt
> Use this file to discover all available pages before exploring further.

# The 837: how claims are told to payers

> What an 837 carries, the three variants, how EHR fields map into it, and where the classic errors originate.

The **837** is the X12 transaction that carries a healthcare claim from a provider to a payer. It says who is billing, who rendered the service, who the patient is, what was done, why it was done, and what is being charged. Three variants exist, **837P** for professional, **837I** for institutional, and **837D** for dental.

## The three variants

|                        | 837P                                         | 837I                                          | 837D                                                         |
| ---------------------- | -------------------------------------------- | --------------------------------------------- | ------------------------------------------------------------ |
| **Who uses it**        | Physicians, NPs, therapists, most outpatient | Hospitals, facilities, SNFs                   | Dentists                                                     |
| **Paper analogue**     | CMS-1500                                     | UB-04                                         | ADA Dental Claim Form                                        |
| **Procedure codes**    | CPT / HCPCS                                  | CPT/HCPCS + revenue codes                     | CDT                                                          |
| **Distinctive fields** | Place of service, rendering provider         | Revenue codes, bill type, admission data, DRG | Tooth numbers, surfaces, quadrants, oral cavity designations |

<Note>
  🦷 **Dental**, 837D is not "837P with different codes." It carries tooth-level detail that has no professional-claim equivalent, and dental payers apply benefit rules (annual maximums, frequency limits, missing-tooth clauses) that produce denial patterns unlike medical ones.
</Note>

<Note>
  🩺 **Medical**, an MSO-PC group with an outpatient surgery center or a facility component may need 837I as well. Confirm your clearinghouse supports every format you'll send.
</Note>

## What an 837 carries

Six categories of information:

### 1. Submitter and receiver

Who transmitted the file and who it's for. Set by your clearinghouse configuration — this is where a misconfigured multi-entity setup sends claims under the wrong PC.

### 2. Billing provider (Loop 2000A / 2010AA)

**Your professional entity.** Legal name, NPI (Type 2), Tax ID, address, and taxonomy.

Everything here must match what the payer holds from enrollment **exactly**. The legal name must match your IRS EIN letter and your W-9. The NPI must be the one you enrolled. The taxonomy must match the taxonomy on your contract. Name and taxonomy mismatches are the leading cause of first-claim rejections, and they are enrollment problems wearing a billing costume.

### 3. Rendering, referring, and supervising providers (Loops 2310A–D)

The **rendering provider** is the individual clinician who performed the service, identified by Type 1 NPI. Where a **referring provider** is required, common for diagnostics and specialty services, omitting it is a denial. **Supervising provider** appears in incident-to and supervision scenarios.

### 4. Subscriber and patient (Loops 2000B / 2000C)

The **subscriber** holds the policy; the **patient** may be the subscriber or a dependent. Member ID, name, date of birth, gender, address, and relationship code.

Precision matters more than it feels like it should: transposed member ID digits, a missing alpha prefix on a Blues ID, a nickname instead of the legal name, or a date of birth that differs from the payer's record all produce rejections.

### 5. Claim level (Loop 2300)

Total charge, place of service, claim frequency code (original, corrected, void), prior authorization number, and up to twelve **diagnosis codes** in the `HI` segment.

### 6. Service lines (Loop 2400)

One per procedure. Each carries the procedure code and up to four modifiers, the charge, units, the service date, and **diagnosis pointers** linking that line to the diagnoses that justify it.

## How EHR fields map in

Practically, most 837 errors are data-entry or configuration errors upstream:

| EHR field           | 837 destination            | Common failure                                   |
| ------------------- | -------------------------- | ------------------------------------------------ |
| Practice legal name | Billing provider name      | Brand entered instead of legal name              |
| Group NPI           | Billing provider NPI       | Wrong entity's NPI in a multi-PC group           |
| Tax ID              | Billing provider ID        | Doesn't match the W-9 on file                    |
| Group taxonomy      | Billing provider taxonomy  | Doesn't match the enrolled taxonomy              |
| Provider record     | Rendering provider NPI     | Clinician not credentialed with this payer       |
| Insurance record    | Subscriber ID              | Missing alpha prefix, transposed digits          |
| Encounter POS       | Claim place of service     | Telehealth 02 vs 10 confusion                    |
| Auth field          | Prior authorization number | Auth obtained but never entered → CARC 197       |
| Diagnosis list      | HI segment                 | Order matters; principal diagnosis first         |
| Charge line         | SV1 with pointers          | Modifier missing; pointer to the wrong diagnosis |

## For CMS-1500 veterans

If you learned billing on paper, the mental translation:

| CMS-1500 box                 | 837P location           |
| ---------------------------- | ----------------------- |
| Box 24A–24J (service lines)  | Loop 2400               |
| Box 21 (diagnoses)           | Loop 2300, `HI` segment |
| Box 24E (diagnosis pointer)  | `SV107` composite       |
| Box 33 (billing provider)    | Loop 2010AA             |
| Box 24J (rendering provider) | Loop 2310B              |
| Box 17 (referring provider)  | Loop 2310A              |
| Box 23 (prior auth)          | Loop 2300, `REF*G1`     |
| Box 24B (place of service)   | `CLM05` composite       |

The important shift: the paper form has a fixed grid with a hard cap on service lines. The 837 has **loops that repeat**, so a claim can carry far more detail, and correspondingly more ways to be wrong.

## Where errors originate

Ranked by how often they cause first-submission failures:

1. **Enrollment data mismatches**, name, NPI, Tax ID, taxonomy not matching the payer's records
2. **Provider not credentialed** or not linked to the group contract
3. **Subscriber ID errors**, the single most common patient-data failure
4. **Missing prior authorization number**, obtained but not captured
5. **Place of service errors**, especially telehealth 02 vs 10
6. **Missing or wrong modifiers**, 25 and 59 lead the list
7. **Diagnosis pointer errors**, line pointing at a diagnosis that doesn't support it
8. **Missing referring provider** where required
9. **Date of service before the provider's effective date**
10. **Duplicate submission** instead of a corrected claim

Note that items 1, 2, and 9 are **enrollment** problems and item 4 is a **workflow** problem. Only 5–7 are properly billing errors.

## Corrected claims

To fix a claim already adjudicated, resubmit with the appropriate **claim frequency code** (7 for replacement, 8 for void) and the **original claim reference number**.

<Warning>
  **Never resubmit a denied claim as a new original claim.** It will deny as a duplicate (CARC 18), you'll have burned the time, and you may run out the correction window. Use the frequency code and reference the original.
</Warning>


## Related topics

- [Step 10: Submit your first claim](/start/zero-to-paid/submit-your-first-claim.md)
- [Submit clean claims](/guides/billing/submit-clean-claims.md)
- [EDI and X12, gently](/concepts/payments/edi-and-x12-basics.md)
- [The life of a claim](/concepts/payments/claim-lifecycle.md)
- [The 835: how payers answer](/concepts/payments/understanding-835s.md)
- [837 file anatomy](/reference/edi/837-anatomy.md)
- [Place of service codes](/reference/edi/place-of-service-codes.md)
- [Provider taxonomy codes](/reference/edi/taxonomy-codes.md)