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Claim adjustment reason code

CO-107: Related or qualifying claim not identified

CO-107 means: The related or qualifying claim/service was not identified on this claim. This service only pays when it is linked to another one, and the link is missing from the claim.

Read the group code before you act on this

107 is the claim adjustment reason code. The CO in front of it is the group code — a separate field the payer sets on the remittance. The same reason code arrives under different group codes depending on the payer and the situation, and the group code, not the reason code, decides who owes the money.

CO — contractual obligation. You write it off. You may not bill the patient.
PR — patient responsibility. Billable to the patient.
OA — other adjustment, and PI — payer initiated reduction. Neither is patient responsibility.

What causes it

An add-on code was billed without its primary procedure on the claim
The primary procedure was billed on a separate claim, so the payer cannot see the pair
The qualifying service was performed by another provider and no reference was included
An assistant surgeon or co-surgeon line has no corresponding primary surgical line

How to work it

Identify what the qualifying service is — the code descriptor for an add-on code names its primary explicitly
Where both were performed, rebill them together on one claim rather than appealing separately
Where the primary was billed on an earlier claim, submit with the reference to it that the payer requires
Where no qualifying service exists, the add-on code should not have been billed at all

How to stop it recurring

Add-on codes should never leave the practice unaccompanied. A scrubber rule that refuses to submit one without its primary removes this denial almost entirely.

Who does this work

A charge entry & claim submission seat at $1,500 per seat per month works this queue full time, during your business hours, inside your own system. Every call is logged with the payer reference number and the outcome, and every Friday you get it in writing.

What that seat does →

Codes worked the same way

CO-107 is fixed in credentialing, not on the claim. So are these, which is why a queue sorted by recovery route moves faster than one sorted by code number — the same person, in the same system, with the same evidence to hand, clears all of them in one pass.

CO-B7 — Provider not eligible that day
CO-185 — Rendering provider not eligible
CO-8 — Procedure and provider type disagree
CO-183 — Referring provider not eligible
CO-184 — Ordering provider not eligible
CO-242 — Provider out of network

Specialties that name this among their costliest

These are specialties whose own worst denials include one of this kind. The line under each is the denial they name, quoted from their page so you can see what the link is based on.

Pediatrics
Newborn claims denied because the baby was never added to the policy inside the enrollment window
Pulmonology and Critical Care
Sleep study interpretation billed without the qualifying supervision or credentials

What leaving it costs

Working a denied claim costs $57.23 per denied claim in administrative time. Source. At 100 denials a month — an illustration, not a measurement of your practice — that is $5,723 a month, or $68,676 a year, in labour alone.

The figure that makes it worth spending: about 90% of initially denied claims are eventually paid. Source. The reason a denial sits is almost never that nobody knows how to work it — it is that nobody has the hours.

Questions

What does denial code CO-107 mean?

The related or qualifying claim/service was not identified on this claim. In plain terms: This service only pays when it is linked to another one, and the link is missing from the claim.

What causes CO-107?

An add-on code was billed without its primary procedure on the claim. The primary procedure was billed on a separate claim, so the payer cannot see the pair. The qualifying service was performed by another provider and no reference was included. An assistant surgeon or co-surgeon line has no corresponding primary surgical line.

How do you fix a CO-107 denial?

Identify what the qualifying service is — the code descriptor for an add-on code names its primary explicitly. Where both were performed, rebill them together on one claim rather than appealing separately. Where the primary was billed on an earlier claim, submit with the reference to it that the payer requires. Where no qualifying service exists, the add-on code should not have been billed at all.

Can CO-107 be prevented?

Add-on codes should never leave the practice unaccompanied. A scrubber rule that refuses to submit one without its primary removes this denial almost entirely.

Is CO-107 the same as PR-107?

Same reason, different group code. The number 107 is the reason: This service only pays when it is linked to another one, and the link is missing from the claim. The prefix says who carries the amount. CO means contractual obligation — the payer says the amount is not billable to anybody, and it is written off unless the denial itself is overturned. PR-107 is the same reason assigned to patient responsibility — the payer says the amount is owed by the patient, and it is billed to them. Read the prefix before the number: it decides whether you appeal, write off, or bill the patient.

What about the codes next to CO-107?

CO-106 and CO-108 are separate codes and this site does not yet cover them. The authoritative list is the X12 Claim Adjustment Reason Codes at x12.org/codes/claim-adjustment-reason-codes; a code is only described here once its official text, causes and fix have been written and checked.

Code descriptions are the standard X12 claim adjustment reason and remittance advice remark code text. Payer policies differ, and the payer’s own coverage policy governs any individual claim. This page is working guidance, not legal or clinical advice.

Last updated 2026-09-12. This is operational guidance drawn from payer remittance practice, not legal, coding or reimbursement advice. Payer-specific rules vary and change; confirm against the payer’s own policy before acting on a specific claim.

Written by Ibtesam Asif · Last reviewed 2026-09-12

Code descriptions are the standard published text. Everything after them is operational guidance from our own work, and payer policy governs any individual claim.

Other denial codes

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