Denial code · group CO
CO-15: Authorization number missing or not matched to the service; X12 retired this code in 2018
Short answer
CO-15 meant the authorization number on the claim was missing, invalid, or did not apply to the service or provider billed. X12 deactivated the code with a stop date of May 1, 2018, so a current remittance should carry CO-197, CO-198 or CO-16 with M62 instead. If a payer still sends it, treat it as a CO-197: find the approval, match it to the claim, and send a corrected claim with the right number.
Look up other codes in the denial code library.
Last reviewed by the Remitwright billing team. Editorial policy
Group CO means contractual obligation: the balance is written off, not billed to the patient. The number is the reason; the two-letter group says who carries the balance.
Remark codes that usually come with CO-15
- M62
- The treatment authorization code is missing, incomplete or invalid
- N54
- The claim does not match the services that were precertified or authorized
Common causes
A payer still mapping to a retired code
X12 stopped CARC 15 in 2018, but a payer's adjudication system or a clearinghouse translation table can keep producing it. The denial is real; only the label is out of date. Ask the payer which current code it means so your denial reports group it with the right work queue.
The authorization number never reached the claim
The number sits in the chart or the authorization tracker while the prior authorization field on the 837P is blank, or a referral number went in its place. Payers match on the number first and look at the member second, so a blank field reads as no approval.
The number does not apply to this service or provider
Approval obtained under one NPI or tax ID with the claim billed under another, a code on the claim that is not on the approval, or a date of service outside the approved span. N54 usually rides along with this version.
The number was mangled on the way out
Leading zeros dropped, a trailing letter cut off by a field length limit, or two authorization numbers run together on a claim with several services. The payer cannot find a match and reports the number as invalid.
How to fix it and resubmit
- 1
Translate the code first
Check the 835 for a remark code and the payer's remittance guide. M62 means the number is the problem; N54 means the details do not match. Then work it under the current code the payer intends, CO-197 or CO-198 for most plans, so the fix follows the right process.
- 2
Find the approval and compare it to the claim
Pull the authorization letter or portal record and check member, provider, codes, units and dates against the 837P. Each mismatch has a different fix: a corrected claim for a claim error, an amendment request for an approval error.
- 3
Corrected claim with the full number
Enter the complete authorization number in the prior authorization field, in the format the payer's system expects, and resubmit with frequency code 7 and the original claim number. Check that the number survives the clearinghouse by reading the outbound file, not the screen.
- 4
Amend or appeal when the approval itself is short
Ask the payer to extend the dates, add the code or correct the provider on the existing approval. If the plan refuses and the service was medically necessary, file an appeal with the record and the approval history.
How to prevent it
- Authorization numbers, approved codes, units and date spans stored in the practice management system so they flow to the claim without rekeying
- A scrubber hold on any authorization-required code where the prior authorization field is blank or shorter than the payer's number format
- A denial code map that routes CO-15 into the same queue as CO-197 and CO-198, so the retired label does not hide authorization problems
- A reconciliation of billed codes against approved codes before the claim leaves, whenever the clinician changes the plan of care
A CO-15 from a plan with an old code table
A home care agency bills skilled nursing visits to a small regional plan and receives CO-15 with M62 on every line. The plan has not updated its remittance codes since X12 retired CARC 15. The agency's practice management system had cut the authorization number to twelve characters, dropping the final letter. The biller resubmits with the full number using frequency code 7 and the claims pay. The agency also changes its denial map so CO-15 lands in the authorization queue next to CO-197. This is a hypothetical example.
Official text: the X12 claim adjustment reason code list. The meaning above is our paraphrase for billers; the list is the authority.
FAQ
Questions about CO-15
Is CO-15 still a valid denial code?
Which code replaced CO-15?
The authorization is approved. Why did the claim deny?
Can I bill the patient after a CO-15?
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