CO-22
CO · Contractual Obligation
CO-22 Denial Code: Another payer may be primary under coordination of benefits
The payer believes another insurer may be primary or shares responsibility. The claim must go to the correct primary payer first.
- Group code
- CO - Contractual Obligation
- Code type
- CARC
- Billable to patient?
- No - rebill the correct/primary payer
- Appealable?
- No - rebill to the correct payer
- Category
- Coordination of Benefits
- Common pairing
- MA04
On a remittance
CAS*CO*22*125.00On a paper EOB it shows as CO-22.What CO-22 means
CO-22 is a coordination-of-benefits (COB) denial. The payer you billed thinks it is not the primary payer, or that another plan should pay first. You generally must submit to the primary payer and then bill this payer as secondary with the primary's explanation of benefits attached. In practice this code is sometimes issued under group OA (OA-22) rather than CO, depending on the payer.
Common causes
- Another insurance is primary and was not billed first.
- The payer's COB records are outdated (old or terminated other coverage on file).
- Medicare Secondary Payer (MSP) rules apply and were not followed.
- The patient has dual coverage and the order of benefits was not established.
How to fix it
- Identify the correct primary payer and submit there first.
- Once the primary adjudicates, bill this payer as secondary with the primary EOB/remittance attached.
- If the COB record is wrong, have the patient update coordination of benefits with the payer, then resubmit.
- For MSP situations, confirm the correct primary using the MSP questionnaire.
How to prevent it
- Capture all coverage and establish the order of benefits at registration.
- Verify primary vs. secondary status during eligibility checks.
- Prompt patients to keep COB information current with their payers.
No - rebill to the correct payerCorrectable rather than a true appeal: bill the correct primary first, then resubmit as secondary. Appeal only if this payer truly is primary and its COB record is wrong.
Dispute / correction letter
Fill in the bracketed fields, attach your supporting documentation, and send through the payer's correction or dispute channel. This is a starting point — adjust to your payer's requirements.
Re: Coordination of Benefits (CO-22) - Claim [Claim Number] Patient: [Patient Name] | Member ID: [Member ID] Date(s) of Service: [DOS] To Whom It May Concern: Claim [Claim Number] was denied under CO-22 (coordination of benefits). [Choose: Our records show your plan is primary for this patient effective [Date]; the other coverage on file terminated on [Date]. / The primary payer has adjudicated and the EOB is enclosed.] We request that you process this claim as the [primary/secondary] payer. Supporting coverage documentation is enclosed. Sincerely, [Your Name], [Practice Name] | [Phone] | [NPI/TIN]