> ## 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.

# Group codes (CO, PR, OA, PI)

> Who owes what: the four X12 claim adjustment group codes, and why miscoding them corrupts patient balances.

**Group codes** appear in the `CAS` segment of the 835, immediately before the CARC. There are four, and they answer one question: **who bears this dollar?**

## The four codes

| Code   | Name                           | Means                                                      | Your action                                         |
| ------ | ------------------------------ | ---------------------------------------------------------- | --------------------------------------------------- |
| **CO** | **Contractual Obligation**     | The provider absorbs it under the contract                 | **Write it off.** You may **not** bill the patient. |
| **PR** | **Patient Responsibility**     | The patient owes it                                        | **Bill the patient.**                               |
| **OA** | **Other Adjustment**           | Neither of the above, usually informational, or a transfer | Depends; often a transfer to a secondary payer      |
| **PI** | **Payer Initiated Reductions** | The payer's own decision, not contractual                  | Often **appealable**                                |

## Why this is the highest-stakes field in the 835

**Group code mapping determines your patient ledger.**

* **Posting a PR amount as CO** means you never bill a patient who owes you money. Pure, silent revenue loss, and it doesn't show up in any denial report.
* **Posting a CO amount as PR** means you bill a patient for something your contract says they don't owe. That is balance billing: a contract breach, a regulatory problem in many states, and a patient complaint.

Test your auto-posting configuration against a real 835 before going live, and re-test after any system change. See [Post payments from 835s](/guides/billing/post-payments-from-835s).

## CO, contractual obligation

The most common group code. The provider absorbs the amount because the participation agreement says so.

| Common pairing | Meaning                                                                      |
| -------------- | ---------------------------------------------------------------------------- |
| **CO-45**      | Charge exceeds the fee schedule. **The standard write-off.**                 |
| **CO-197**     | Authorization absent. **Your failure, not the patient's, cannot bill them.** |
| CO-29          | Timely filing expired                                                        |
| CO-97          | Bundled into another service                                                 |
| CO-253         | Medicare sequestration                                                       |
| CO-18          | Duplicate claim                                                              |

**CO-197 is the one people get wrong.** It is tempting to bill the patient for a service the payer refused over a missing authorization. You cannot — the group code says contractual obligation, meaning the practice bears it. The patient did nothing wrong.

## PR, patient responsibility

The patient owes it. Move it to the patient ledger and into the statement cycle.

| Common pairing | Meaning                                                 |
| -------------- | ------------------------------------------------------- |
| **PR-1**       | Deductible                                              |
| **PR-2**       | Coinsurance                                             |
| **PR-3**       | Copay                                                   |
| PR-96          | Non-covered charge, where the patient is responsible    |
| PR-204         | Not covered under the benefit plan                      |
| PR-227         | Information requested from the patient was not provided |

<Tip>
  For **PR-96** and **PR-204**, whether you can actually collect depends on your contract and on whether the patient received proper advance notice. Confirm before billing.
</Tip>

## OA, other adjustment

Used where neither CO nor PR applies. Frequently informational, or a transfer.

| Common pairing | Meaning                                                             |
| -------------- | ------------------------------------------------------------------- |
| **OA-23**      | The impact of prior payer adjudication, appears on secondary claims |
| OA-22          | May be covered by another payer                                     |
| OA-100         | Payment made to the patient, you recover from them                  |
| OA-94          | Processed in excess of charges                                      |

## PI, payer initiated reductions

The payer reduced payment based on its own determination, not a contractual term. **These are the most likely to be appealable**, because there is a payer decision to contest rather than a contract term to accept.

Less common than the other three. When you see PI, look at it, it often represents a determination worth challenging.

## Quick reference: can I bill the patient?

| Group code | Bill the patient?                      |
| ---------- | -------------------------------------- |
| **CO**     | **No**, ever                           |
| **PR**     | **Yes**                                |
| **OA**     | Depends, read the CARC                 |
| **PI**     | Usually no; consider appealing instead |

## Configuration checklist

For your auto-posting setup:

* [ ] **CO** → contractual adjustment write-off account
* [ ] **PR** → patient ledger, into the statement cycle
* [ ] **OA-23** on a secondary claim → informational, not an adjustment
* [ ] **OA-100** → patient recovery workflow
* [ ] **PI** → review queue, not auto-write-off
* [ ] **Any group code with a \$0 payment and a denial CARC** → denial queue, **not** write-off
* [ ] **PLB segments** → handled separately from claim-level adjustments

<Warning>
  **Never auto-write-off a denial.** A \$0-paid line with a denial CARC goes to the denial queue with a root-cause tag. Auto-writing them off is how practices silently lose recoverable revenue. See [Work the denial queue](/guides/billing/work-the-denial-queue).
</Warning>

## A note on RARC MA13

If you see **MA13** on a remittance — "you may be subject to penalties if you bill the patient for amounts not reported with patient responsibility group code" — treat it as a direct warning that your group code handling is being watched. Check your mapping.


## Related topics

- [The 835: how payers answer](/concepts/payments/understanding-835s.md)
- [Deductibles, copays, coinsurance, and patient balances](/concepts/payments/patient-responsibility.md)
- [Post payments from 835s](/guides/billing/post-payments-from-835s.md)
- [Work the denial queue](/guides/billing/work-the-denial-queue.md)
- [CARC codes (Claim Adjustment Reason Codes)](/reference/edi/carc-codes.md)
- [RARC codes (Remittance Advice Remark Codes)](/reference/edi/rarc-codes.md)
- [835 file anatomy](/reference/edi/835-anatomy.md)