Claim adjustment codes · X12 CARC, RARC and group codes
Claim adjustment code lookup: CO-45, PR-1, 97, N130.
A remittance adjustment has two parts: a group code (CO, PR, OA or PI) that says who is responsible, and a reason code (CARC) that says why. Type both, like CO-45, to read the pair.
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How to read an adjustment on a remittance
An 835 remittance or a paper explanation of payments lists each adjustment as a group code, a reason code and an amount. For example, CO-45 $80.00 means a contractual obligation adjustment, reason 45, eighty dollars. A claim adjustment reason code (CARC) says why the payment differs from the charge. A remittance advice remark code (RARC), such as N130, adds detail. Both lists are maintained by X12; the group codes are CO, OA, PI and PR.
The four group codes
| Group | X12 name |
|---|---|
| CO | Contractual Obligation |
| OA | Other Adjustment |
| PI | Payor Initiated Reduction |
| PR | Patient Responsibility |
X12 publishes only the names. How each group affects who may be billed is set by payer rules and your contract; the common reading is that CO is written off and PR belongs to the patient. When the group code and the reason look inconsistent, ask the payer.
Codes explained on this tool
The lookup above covers the codes below, with the X12 wording and a plain-language line. The code-by-code pages below add a worked example and next steps.
| Code | X12 text |
|---|---|
| CARC 1 | Deductible Amount |
| CARC 2 | Coinsurance Amount |
| CARC 3 | Co-payment Amount |
| CARC 4 | The procedure code is inconsistent with the modifier used. |
| CARC 16 | Claim/service lacks information or has submission/billing error(s). |
| CARC 18 | Exact duplicate claim/service (Use only with Group Code OA except where state workers' compensation regulations requires CO) |
| CARC 22 | This care may be covered by another payer per coordination of benefits. |
| CARC 27 | Expenses incurred after coverage terminated. |
| CARC 29 | The time limit for filing has expired. |
| CARC 45 | Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement. |
| CARC 50 | These are non-covered services because this is not deemed a 'medical necessity' by the payer. |
| CARC 96 | Non-covered charge(s). At least one Remark Code must be provided (may be comprised of either the NCPDP Reject Reason Code, or Remittance Advice Remark Code that is not an ALERT.) |
| CARC 97 | The benefit for this service is included in the payment/allowance for another service/procedure that has already been adjudicated. |
| CARC 109 | Claim/service not covered by this payer/contractor. You must send the claim/service to the correct payer/contractor. |
| CARC 119 | Benefit maximum for this time period or occurrence has been reached. |
| CARC 197 | Precertification/authorization/notification/pre-treatment absent. |
| CARC 204 | This service/equipment/drug is not covered under the patient's current benefit plan |
| RARC N130 | Consult plan benefit documents/guidelines for information about restrictions for this service. |
Code by code, with next steps
- CARC 4
- CARC 16
- CARC 18
- CARC 29
- CARC 45
- CARC 50
- CARC 97
- CARC 109
- CARC 119
- CARC 197
- Modifier 25 and modifier 59, the modifiers behind many CARC 4 and 97 denials
RARC N130
X12 words RARC N130 as: "Consult plan benefit documents/guidelines for information about restrictions for this service." It is a pointer. Open the plan's benefit documents or provider manual for the limit it refers to; the remark itself does not say which restriction applies. Read it together with the CARC on the same line, which tells you what the payer did.
What is not here
The full CARC list has about 300 entries and the RARC list over a thousand, and X12 owns the copyright and updates them regularly. This tool shows the wording only for the codes listed, so use the official X12 pages in the sources for any other code. Place of service and the claim setting are covered in the place of service codes list.
Sources
- X12: Claim Adjustment Reason Codes — code text, start and last-modified dates (list dated 10/30/2026, retrieved 2026-11-01)
- X12: Claim Adjustment Group Codes — CO, OA, PI, PR names (retrieved 2026-11-01)
- X12: Remittance Advice Remark Codes — RARC N130 wording and start dates (retrieved 2026-11-01)
Every code description and rule above was retrieved from these pages on November 1, 2026. Payers revise code lists, contracts and policies, so confirm anything that affects a claim or a deadline with the payer.
Frequently asked questions
What is the difference between a CARC and a RARC?
A CARC (claim adjustment reason code) says why the payer adjusted an amount. A RARC (remittance advice remark code) adds detail or a next step. Many adjustments carry both.
What does CO-45 mean?
CO is the group code Contractual Obligation, and 45 is the reason: charge exceeds fee schedule or contracted arrangement. It is normally a write-off, not a bill to the patient.
What is the difference between CO and PR?
X12 names CO Contractual Obligation and PR Patient Responsibility. In practice CO is written off by the provider and PR is an amount the patient may owe.
Where is the full list of codes?
On the X12 website, which maintains the CARC, RARC and group code lists. Links are in the sources.
Not legal, billing or medical advice
This page explains published code lists and rules and runs a lookup in your browser. It cannot see your claim, your contract or any payer's policy. Confirm with the payer or your Medicare Administrative Contractor before you resubmit, appeal or bill a patient.