CO-22 Denial Code: Coordination of Benefits, Fixed

CO-22 means the payer believes another insurance plan should pay first. Under coordination of benefits (COB), the payer you billed thinks it is secondary, or its records show other coverage. You fix it by confirming which plan is primary, billing in the right order, and getting the payer's COB record corrected.

1. What CO-22 means

CO (Contractual Obligation): the provider cannot bill the patient for this adjustment.
22: this care may be covered by another payer per coordination of benefits.

CO-22 is rarely a final answer. It is the payer saying "not us first". The money is usually recoverable once the claim goes to the right primary payer, as long as you stay inside both payers' filing limits.

2. Why CO-22 happens

The patient has other coverage you did not know about: a spouse's employer plan, a new job, or Medicare.
The payer's COB file is out of date. The other coverage ended, but the payer still shows it as active.
The plans were billed in the wrong order, for example Medicare billed first when an employer group plan is primary.
The payer is waiting on a COB questionnaire from the member and pends or denies claims until it arrives.
Accident or liability coverage applies, such as auto insurance or workers' compensation.

3. Who pays first: common COB rules

Situation	Usually primary
Patient has their own employer plan and is also a dependent on a spouse's plan	The patient's own employer plan
Child covered by both parents' plans (parents married or living together)	The plan of the parent whose birthday comes first in the calendar year (the "birthday rule")
Medicare patient who is still working, employer has 20 or more employees	The employer group health plan
Medicare patient under 65 with a disability, employer has 100 or more employees	The large group health plan
Patient with ESRD covered by a group plan	The group plan during the 30-month coordination period, then Medicare
Patient has both Medicare and Medicaid	Medicare (Medicaid is the payer of last resort)
Injury from a car accident or at work	Auto, no-fault, or workers' compensation coverage, depending on the case

These are the common rules, not every rule. Divorce decrees, COBRA, and state laws change the order in specific cases. Medicare's Secondary Payer rules and each plan's COB provisions are the authority.

4. How to fix a CO-22 denial

Ask the patient about all current coverage, and get copies of every card.
Check eligibility with each payer. The eligibility response often shows other coverage on file. For Medicare, check the beneficiary's MSP information.
If another plan is primary, bill it first, then send the claim to the secondary payer with the primary's payment details.
If the payer's COB record is wrong, the member usually has to update it with the plan (by phone or a COB form). Then ask the payer to reprocess the claim.
Watch both filing limits. The primary payer's deadline runs from the date of service. See timely filing limits by payer.

5. How to prevent CO-22

Ask about other coverage at every visit, not just at registration. Coverage changes with jobs, marriages, and turning 65.
Use a Medicare Secondary Payer questionnaire for Medicare patients.
Read the "other coverage" section of the eligibility response before the visit. Our eligibility verification guide shows where it appears.
Track CO-22 by payer. A payer that keeps denying with stale COB data is worth a call to your provider rep.

Related: CARC and RARC codes list, OA-23 (how primary payments show on secondary claims), and CO-16.

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Frequently asked questions

What does denial code CO-22 mean?

The payer believes another insurance plan should pay first under coordination of benefits. The provider cannot bill the patient for the adjustment; the claim should go to the primary payer.

How do I fix a CO-22 denial?

Confirm all of the patient's coverage, bill the correct primary payer first, then bill the secondary with the primary's payment details. If the payer's COB record is wrong, the patient usually has to update it with the plan before the claim is reprocessed.

What is the birthday rule?

For a child covered by both parents' plans, the plan of the parent whose birthday falls earlier in the calendar year is usually primary. The year of birth does not matter. Custody arrangements and court orders can change this.

Is Medicare primary or secondary?

It depends. Medicare is usually secondary when the patient is covered by an employer group plan through current employment at an employer with 20 or more employees. It is primary when the patient is retired. Medicaid is always the payer of last resort.

Can I bill the patient for CO-22?

No. CO means the provider is responsible for the adjustment. Bill the correct primary payer instead.

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CO-22 Denial Code: Coordination of Benefits Denials, Explained