CO · Contractual ObligationCARC 107

Denial Code CO-107

Q: What does CO-107 mean?

CO-107 is a Contractual Obligation (CO) denial: "The related or qualifying claim/service was not identified on this claim." This service depends on a related or qualifying claim — a primary procedure, a prior service, or the original claim it adjusts — that wasn't referenced here, so the payer can't connect them.

Q: Is CO-107 the patient's responsibility or a provider write-off?

CO-107 carries the CO group code (Contractual Obligation): Provider/contractual responsibility — not billable to the patient while denied. A CO adjustment is the provider's responsibility, not the patient's: balance-billing the patient for a CO amount is a contract (and often compliance) violation. But CO does not automatically mean “write it off.” When the cause is fixable — missing information (CO-16), a modifier problem (CO-4), or NCCI bundling (CO-97) — you correct and resubmit, or appeal with documentation. You only truly write the amount off when it is a final contractual adjustment, such as the fee-schedule difference on CO-45.

The related or qualifying claim/service was not identified on this claim.

Source: X12 Claim Adjustment Reason Codes (CARC) & Group Codes. Maintained by the D3rx Clinical Billing Team.

What CO-107 means

This service depends on a related or qualifying claim — a primary procedure, a prior service, or the original claim it adjusts — that wasn't referenced here, so the payer can't connect them.

Why CO-107 happens

A corrected/replacement claim submitted without the original claim number
An add-on or related service billed without referencing its primary procedure
A post-operative or global-period service not linked to the qualifying surgery
An adjustment or void missing the original reference number

What to do when you get CO-107

1Identify the related or qualifying service the payer is looking for
2Add the original/related claim reference in the correct field (e.g., box 22 on the CMS-1500 or the 837 reference loop)
3Confirm the claim frequency/type code is correct for a replacement or adjustment
4Resubmit as a corrected claim with the reference populated

Got this denial right now?

Fix & resubmit: see the CO-107 correction steps

See CO-107 correction steps Ask D3 about CO-107

CO-107 clears with a corrected claim, not an appeal. Ask D3 walks you through the exact fix — free, no signup.

CO group code: who absorbs the charge

Contractual Obligation — Provider/contractual responsibility — not billable to the patient while denied.

A CO adjustment is the provider's responsibility, not the patient's: balance-billing the patient for a CO amount is a contract (and often compliance) violation. But CO does not automatically mean “write it off.” When the cause is fixable — missing information (CO-16), a modifier problem (CO-4), or NCCI bundling (CO-97) — you correct and resubmit, or appeal with documentation. You only truly write the amount off when it is a final contractual adjustment, such as the fee-schedule difference on CO-45.

Appeal, correct, or write off CO-107?

CO-107 is a linkage/data fix: add the qualifying claim reference and resubmit, rather than appeal. Appeal only if the related claim WAS referenced correctly and the payer still failed to connect them — then attach proof of both claims.

Timing & deadlines

Resubmit the corrected claim within the payer's timely-filing limit (Medicare 12 months from date of service; commercial ~90-180 days). Flagging it as a correction generally preserves the original filing date.

Example

A replacement claim is sent to fix a coding error but the original claim number is left out of box 22. The payer returns CO-107 because it can't tie the replacement to the original. Adding the reference and resubmitting resolves it.

Prevent CO-107 going forward

Always reference the original claim number on replacement/adjustment claims
Link add-on and related services to their primary procedure
Use the correct frequency code (7 replacement / 8 void) with the original reference
Build a scrubber check for missing original-claim references

Code families most affected

Replacement and adjustment claims
Add-on and related services that depend on a primary procedure
Post-operative/global-period services

Related codes

Denial codes you'll often see alongside CO-107

CO-16 CO-4 CO-97

Payer notes

CO-107 usually rides with a remark code that names the qualifying claim or service. It is a connection problem on the claim, not a coverage decision — nothing about the service's coverage is in dispute.

Fix this CO-107 denial the right way

CO-107 is resolved with a corrected claim, not an appeal. Ask D3 gives you the exact correction steps — free, backed by CMS, Medicare, and major-payer data.

See CO-107 correction steps Ask D3 about CO-107 All denial codes

Medical billing disclaimer

CARC/RARC definitions are the standardized X12 set; group-code semantics follow the X12 Claim Adjustment Group Code standard. Filing and appeal windows vary by payer — the standard anchors shown (Medicare redetermination 120 days from the remittance; Medicare timely filing 12 months from date of service; most commercial payers ~90-180 days) are general references, not a guarantee for any specific plan. Always confirm the rule in the payer's provider manual before acting. D3rx is not responsible for claim outcomes.