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

# What is an 835?

> The X12 835 (the ERA) is the file a payer sends to explain a payment — claim by claim and line by line, what was paid, reduced, or denied, and why.

The 835 (formally the X12N 835 Health Care Claim Payment/Advice, colloquially the **ERA**) is the file a payer sends to explain a payment. One file tells you, claim by claim and line by line, what was paid, reduced, or denied, and why.

HIPAA designates the 835 as the standard electronic remittance format (45 C.F.R. § 162.1602). Every covered payer can produce one. If a major payer sends you paper EOBs, that's an enrollment gap, not a technical limit. See [Enroll in EFT and ERA](/guides/enroll-eft-era).

## Anatomy

```mermaid theme={null}
flowchart TD
    BPR["BPR: the payment<br/>total amount, method, date, payer bank IDs<br/>(BPR10 = payer's originating company ID)"]
    TRN["TRN: trace number<br/>same number rides the ACH addenda<br/>= the reassociation key"]
    CLP1["CLP: claim 1<br/>patient, status, billed, paid"]
    CLP2["CLP: claim 2 ... claim N"]
    SVC["SVC: service lines<br/>per-procedure billed vs paid"]
    CAS["CAS: adjustments<br/>group code + CARC per dollar of difference<br/>must balance: billed = paid + adjustments"]
    PLB["PLB: payment-level adjustments<br/>recoupments, interest, withholds"]
    BPR --> TRN --> CLP1
    CLP1 --> SVC --> CAS
    CLP1 -.-> CLP2
    BPR --> PLB
```

One 835 = one payment. A single \$14,306.22 deposit might cover 40 claims. The parts worth knowing:

* **TRN** links the file to the ACH deposit. When money and remittances won't line up, match on TRN and BPR10. Full story: [EFT reassociation](/concepts/eft-reassociation).
* **CAS** accounts for every dollar between billed and paid, each with a group code (CO contractual, PR patient responsibility) and a [CARC](/concepts/carc-rarc-denial-codes). The math must balance or posting software rejects the file.
* **PLB** is where mysterious shortfalls live. A deposit \$2,400 short of its claims usually has a PLB recouping an old overpayment.

## Why owners should care

**Automation lives on the 835.** Payers on ERA post automatically; payers on paper mean manual keying at real labor cost. **Denials are data.** CAS segments are a structured record of every dollar not collected and the stated reason. Aggregate them and fix the top causes. **It's your audit trail.** In an underpayment dispute, the 835 is the evidence.

## Common failure modes

File arrives but money doesn't, or vice versa: [reassociation problem](/concepts/eft-reassociation). Payment by virtual card falls short of the 835 amount: card fees, see [ERA vs. EOB](/concepts/era-vs-eob). 835 never arrives for a payer: ERA enrollment gap, see the [directory](/reference/payer-enrollment-directory). Paper check with EOB, no 835 at all: [the paper problem](/concepts/lockboxes).

<Note>
  **Lemma aside:** Lemma parses 835s and scanned EOBs, reassociates them with deposits automatically, and can generate 835s from paper EOBs to feed your EHR ([docs](https://docs.getlemma.com)).
</Note>