Retired code · CARC 15
CARC 15 (CO-15): the retired authorization-number code
X12 deactivated CARC 15 in 2018. What it meant, why CO-15 can still turn up, and which current codes now report authorization-number problems on behavioral-health claims.
By the ClaimParrot editorial team · Who we are · Reviewed · 5 min read · 5 cited sources
Quick answer
CARC 15 meant the authorization number on the claim was absent, wrong, or tied to a different service or provider. X12 deactivated it on May 1, 2018, so a new remittance should not use it. If CO-15 still appears, treat it as an authorization mismatch: check the number, the provider and the codes, then send a corrected claim.
| Item | Detail |
|---|---|
| Code | CARC 15 · Deactivated on the X12 list (stop date 2018-05-01); checked October 14, 2026 |
| Plain meaning | A retired X12 code (stopped May 1, 2018) that flagged an authorization number that was absent, wrong, or tied to a different service or provider. |
| Group codes seen | CO (contractual obligation) |
| Common remark codes | M62, N54, N758 |
| Where it shows up in BH | Intensive outpatient (IOP), Residential SUD (ASAM levels), ABA therapy, Outpatient therapy |
| Usual next step | Corrected claim with the right authorization number |
| Related codes | CARC 16, CARC 197, CARC 198 |
What did CARC 15 mean, and is it still valid?
CARC 15 told the provider that the authorization number on the claim was missing, invalid, or belonged to another service or provider. It is no longer valid for new remittances: X12 lists it as deactivated with a stop date of May 1, 2018, and the list names no direct successor.
CMS tells Medicare systems not to use a deactivated code in an original remittance, while still letting it pass in derivative messages that carry codes forward from an earlier transaction. Outdated payer code tables and paper EOBs are other ways a retired code resurfaces.
Which current codes cover what CARC 15 used to report?
X12 names no direct successor, so payers choose among active codes. The active reason codes for authorization problems are 197 (approval absent) and 198 (approval exceeded), both revised on the day 15 was retired. Remark codes M62 (number missing or invalid) and N54 (claim does not match the approval) carry the detail.
| Situation | Active codes that describe it | Usual fix |
|---|---|---|
| Number missing or mistyped | Remark code M62, paired with a reason code such as CARC 16 | Corrected claim with the right number |
| No approval matched to the service | CARC 197 | Find the approval, or appeal |
| Approval for other dates, units or provider | CARC 198; remark code N54 | Reconcile, then correct or appeal |
What does CO-15 mean for who pays?
If CO-15 appears, the provider carries the line, as with any authorization problem the contract makes the provider's job. Because the code is retired, also ask the payer to reissue the adjustment with a current code, so your posting rules, work queues and denial reports stay consistent.
| Group + reason | What it signals | Who usually carries the balance |
|---|---|---|
| CO-15 | Authorization-number problem the provider must fix | Provider, until a corrected claim is accepted |
Which remark codes come with CARC 15?
The current lists pair no remark codes with a retired reason code. These remark codes now carry the same message alongside active reason codes.
| Remark code | What it adds | What to check |
|---|---|---|
| M62 | The treatment authorization number is missing, incomplete or not valid. | The number on the claim against the approval letter |
| N54 | Details on the claim do not match what was pre-certified or authorized. | NPI, codes and dates on the approval versus the claim |
| N758 | The payment was adjusted to match the prior-authorization decision. | What the approval actually granted |
Where does CARC 15 show up in behavioral health?
If CO-15 still shows up on a behavioral-health remittance, look for a paper EOB, an older claim being reprocessed, or a secondary claim carrying another payer's adjustments. The causes underneath are the same authorization-number mismatches that active codes such as 197, 198 and the M62 remark code describe today.
| Care setting | Typical trigger | Check first |
|---|---|---|
| Intensive outpatient (IOP) | Approval issued to the facility NPI, claim billed under the group NPI | Which NPI the approval names |
| Residential SUD (ASAM levels) | Number from the previous approval period reused after an extension | Current approval number and date span |
| ABA therapy | Assessment and treatment approval numbers swapped | The number listed for each code |
| Outpatient therapy | Secondary claim repeating a primary payer's old adjustment | The primary remittance and coordination-of-benefits data |
Corrected claim, reconsideration or appeal: which fits CARC 15?
Fix the number. Confirm which approval covers the dates, provider and codes on the claim, enter that number exactly, and resubmit as a corrected claim. If no approval exists, the problem is really a missing authorization, so follow the CARC 197 route. Ask the payer to stop issuing the retired code.
- 01Pull the approval letter and compare its number, NPI, codes and dates with the claim.
- 02Correct the authorization number and any provider or code mismatch, then resubmit within the filing window.
- 03If the payer still issues CO-15 on new remittances, ask its EDI support to update its code mapping.
What evidence resolves a CARC 15?
Little clinical evidence is needed. The fix rests on the approval record and on what was entered on the claim. If the payer disputes that a valid approval existed, the file becomes the same as for a missing-authorization denial: the approval, call references and proof of notice.
- The approval letter or portal record with its number
- The claim as submitted, showing the number entered
- The NPI and codes the approval covers
- The remittance or EOB showing CO-15 and its date
How do Medicare, Medicaid and commercial plans differ on CARC 15?
No program should issue CARC 15 on new remittances, so the program question is which current codes and clocks apply to the fix. Medicare contractors must use current codes only, and Medicaid's 12-month submission rule limits how long a corrected claim can wait.
| Program | What differs |
|---|---|
| Medicare (Original) | Contractors must use current, valid reason and remark codes on original remittances. |
| Medicaid | States must require claims within 12 months of the date of service, which bounds any correction. |
| Commercial and ERISA plans | Payers draw on the same X12 list; flag a CO-15 on a new remittance to the payer's EDI support. |
CO-15 on a paper EOB for IOP days
A fictional IOP program received a paper EOB from a small payer showing CO-15 on four days. The biller had never seen the code, and the lookup showed it was retired.
The approval had been issued to the program's facility NPI while the claim used the group NPI. The biller corrected the NPI, kept the approval number, resubmitted, and asked the payer which current code it would use going forward.
Names, dates, payers and amounts are invented for illustration.
What a ClaimParrot packet does here
- When CARC 15 needs an appeal rather than a corrected claim, an appeal packet answers the payer's stated reason.
- A person checks every packet: $29, or $99 for level of care, and the first is free (pricing).
- No remittances, records or PHI are sent: just the reason and a de-identified summary (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 CARC 15 still a valid denial code?
No. X12 lists CARC 15 as deactivated, with a stop date of May 1, 2018. For authorization problems the active reason codes are 197 and 198, with remark codes such as M62 and N54 for number and matching problems.
Why would a remittance still show CO-15?
Usually an outdated payer code table, a paper EOB produced outside the standard remittance, or a code carried forward from an earlier transaction. Ask the payer which current code applies.
Do we appeal a CO-15?
Usually not. It reports a data problem, so a corrected claim with the right number is the fix. Appeal only if the payer refuses an approval you can prove covered these dates and services.
How should posting rules handle CARC 15?
Send it to the same authorization-mismatch queue used for CARC 16 with M62, and flag the payer so the retired code can be raised with its EDI team.
Primary sources and references
- Claim Adjustment Reason Codes (CARC) code list · X12 · checked
- Remittance Advice Remark Codes (RARC) 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
- 42 CFR 447.45: Medicaid timely claims payment and the 12-month filing rule · eCFR · checked
General information, not legal or medical advice. Payer rules change; confirm deadlines and requirements in the notice and the plan documents. Read our editorial policy.
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