The rules behind the tool
| Code type | Maintained by | What it tells you | Example |
|---|---|---|---|
| Group code | X12 | Who carries the adjusted amount: provider (CO), patient (PR), payer reduction (PI) or other (OA) | CO |
| Claim adjustment reason code (CARC) | X12 committee; updated three times a year | Why the payer paid less than billed, in one code per adjustment amount | 50 |
| Remittance advice remark code (RARC) | CMS; any payer may use them | Extra detail on the reason, or an alert such as appeal rights | N115 |
What can you type into the lookup?
Type the codes exactly as the remittance or EOB shows them, with or without dashes or spaces: CO-50, co50, 50, PR 96, CO-197 N54 or a remark code alone such as N386. Several codes on one line are read together, the way a payer reports them.
- Group and reason code together: CO-50, PR-96, OA-23
- Reason code alone: 50, 197, CARC 119
- Remark codes: N386, M62, MA130
- A whole line: CO-198 N54 N640
How do you read a denial line on an 835 or an EOB?
Each adjustment on an 835 remittance or paper EOB pairs a group code with a reason code and an amount. Remark codes sit with the service line or the claim. Read all three before choosing a route, and look for a policy or coverage reference the payer may add.
- 01Find the adjustment on the service line: group code, reason code and amount.
- 02Find the remark codes for that line, and any claim-level remark codes such as appeal-rights alerts.
- 03Check the policy reference the payer included, if any, then decide: corrected claim, reconsideration or appeal.
Which reason codes does the lookup explain in depth?
The lookup covers the 16 reason codes behavioral-health billing teams meet most, from medical necessity and authorization to provider eligibility and timely filing. Any other valid-looking code gets an honest answer: not in our library yet, with a link to the X12 list.
| Reason code | Plain meaning |
|---|---|
| CARC 4 | Modifier does not fit the billed procedure |
| CARC 11 | Diagnosis does not support the billed procedure |
| CARC 15 | Retired code for an authorization-number problem |
| CARC 16 | Claim is missing data or has a billing error |
| CARC 29 | Claim reached the payer after its filing deadline |
| CARC 39 | Payer had already refused the approval request |
| CARC 50 | Payer judged the service not medically necessary |
| CARC 96 | Charge falls outside the plan's benefits |
| CARC 97 | Paid as part of another service, not separately |
| CARC 119 | The benefit limit for the period is used up |
| CARC 151 | Payer says the record doesn't support this many services |
| CARC 167 | Plan does not cover the diagnosis billed |
| CARC 170 | Payer won't pay this service from this provider type |
| CARC 185 | Rendering clinician isn't eligible for this service |
| CARC 197 | No approval or required notice on file |
| CARC 198 | Billed more than the approval covered |
Do you need to enter patient information?
No. The lookup needs only the codes, never names, member IDs, dates of birth or claim numbers. It runs entirely in your browser: what you type is not sent to ClaimParrot or anyone else, and it is not stored, so there is nothing to sign up for and nothing to delete.
Decoding CO-197 with M62 on a PHP claim
A biller at a fictional PHP program sees CO-197 with remark code M62 on five lines. The lookup explains that CO puts the balance on the provider, that 197 means no approval was matched to the claim, and that M62 points at the authorization number field.
The biller checks the portal, finds the approval under the program's other NPI, corrects the claim and resubmits it. No appeal letter is needed.
Names, dates, payers and amounts are invented for illustration.
What a ClaimParrot packet adds
- Most lines the lookup explains are fixed with a corrected claim. For the ones that need a letter, an appeal packet answers the payer's stated reason.
- Each packet holds an appeal letter draft, an evidence checklist and a deadline plan, checked by a person; the first packet is free (pricing). No remittances or PHI are sent (Trust & security).
Every draft is reviewed and approved by your team. ClaimParrot does not make medical-necessity determinations or give legal advice.
Frequently asked questions
Is CO-50 the same as PR-50?
Same reason, different payer of the balance. Both say the service was found not medically necessary. CO means the provider writes it off; PR means the patient may be billed, which in Medicare requires a valid advance notice signed before the service.
Why does the lookup not know a code from my remittance?
It explains in depth only the 16 reason codes most common on behavioral-health claims and the remark codes that travel with them. For anything else it says so and links the X12 list, rather than guessing.
Can I paste a whole 835 file into the lookup?
No, and you should not paste member details anywhere you do not control. Type only the codes from the line, such as CO-198 N54. The lookup reads codes, not files.
Does the lookup decide whether to appeal?
It shows the usual next step for each code, such as a corrected claim for missing data or an appeal for medical necessity. The decision stays with your team after checking the record, the authorization and the denial notice.
Primary sources and references
- Claim Adjustment Reason Codes (CARC) code list · X12 · checked
- Remittance Advice Remark Codes (RARC) code list · X12 · checked
- Claim Adjustment Group Codes code list · X12 · checked
- Medicare Claims Processing Manual, Chapter 22, §60: group, reason and remark codes on the remittance advice · CMS · checked
- CMS Change Request 14293 (Transmittal 13481): CORE 360 uniform use of CARCs, RARCs and group codes · CMS · checked
- Medicare Claims Processing Manual, Chapter 1, §70 (timely filing) and §80.3 (incomplete or invalid claims) · CMS · checked
General information, not legal or medical advice. The denial notice, the plan documents and state law control; state law can give more time or more rights than the federal floor shown here. Read our editorial policy.
Doing this for every denial in the queue?
Send one de-identified denial and get the appeal letter draft, evidence checklist and deadline plan back, checked by a person before it reaches you. $29 per appeal packet, $99 per level-of-care packet; your first packet is free.