What does denial code CO-22 mean?

CO-22 means the payer believes another insurer is primary under coordination-of-benefits rules and should adjudicate the claim first. Identify the correct primary payer, bill them, then submit to the secondary with the primary's EOB.

Can I bill the patient for CO-22?

No. CO-22 is a contractual adjustment on this claim. The balance belongs to the correct primary payer, not the patient. Billing the patient before coordination is resolved is a common compliance error.

CO-22: Care may be covered by another payer per coordination of benefits

CO-22 is a coordination-of-benefits denial: the payer you billed thinks it is secondary. It is rarely a claim error and almost always a stale eligibility record - either yours or the payer's. Resolving it means establishing the correct payer order, which sometimes requires the patient to update their COB information directly with the insurer.

What it means: The payer believes another insurer is primary for this patient and wants that insurer to adjudicate first.
Who pays the balance: Contractual on this claim - the balance moves to the correct primary payer, not the patient.
Group code CO: Contractual Obligation - the provider absorbs the balance and cannot bill the patient

Why CO-22 happens

The patient has two active policies and the birthday rule or an employer-plan rule makes the other one primary.
The patient is Medicare-eligible but still actively employed with group coverage, making the group plan primary under MSP rules.
A workers' compensation or auto liability claim is open for the same condition.
The payer's COB record is out of date because the patient never responded to its annual COB questionnaire.
The patient recently changed jobs and both the old and new policies show as active.

How to fix a CO-22 denial

1
Re-verify eligibility for the date of service
Run an eligibility check that returns COB order rather than relying on the card. The response usually names the primary payer.
2
Bill the correct primary payer first
Submit to the primary, wait for its remittance, then bill the secondary with the primary's EOB attached in the appropriate loop.
3
If your record is right and the payer's is wrong, escalate the COB record
Ask the patient to call the payer's COB unit to confirm they have no other coverage. Providers usually cannot update a COB record on the patient's behalf; the correction has to come from the member.

Preventing CO-22 denials

Ask about other coverage at every registration, not just at the first visit.
Screen Medicare patients for active group health coverage as part of intake.
Capture accident and employment-relatedness at scheduling so liability claims route correctly from the start.

CO-22 frequently asked questions

What does denial code CO-22 mean?: CO-22 means the payer believes another insurer is primary under coordination-of-benefits rules and should adjudicate the claim first. Identify the correct primary payer, bill them, then submit to the secondary with the primary's EOB.
Can I bill the patient for CO-22?: No. CO-22 is a contractual adjustment on this claim. The balance belongs to the correct primary payer, not the patient. Billing the patient before coordination is resolved is a common compliance error.

Related denial codes

OA-23 CO-109 PR-204

Denial code explanations are original plain-English summaries written for reference and are not the official X12 code descriptions. Payer handling of any code varies by contract - always verify against the remittance advice and your payer agreement before adjusting a claim.