CO-22: Care Covered by Another Payer (COB)

What Does CO-22 Mean?

CO-22 is the standard pairing for this denial. The CO designation means this adjustment is a contractual write-off while the COB issue is being resolved — you cannot bill the patient for the CO-22 amount. The payer is not denying coverage for the service; they are refusing to process as primary because another insurer holds that position. Once you submit to the correct primary payer and then follow up with this secondary payer using the primary's EOB, the claim should process normally.

When CARC 22 appears on a remittance, the payer is telling you that they believe another insurance carrier should process this claim first under coordination of benefits (COB) rules. The payer is not saying the service is not covered — they are saying they are the wrong payer to be billed at this point in the sequence. Until the correct primary payer adjudicates the claim, the secondary (or tertiary) payer will not process it.

This is one of the most common COB-related denials in medical billing and arises from the complexity of patients holding multiple active insurance policies. The typical triggers include submitting to the secondary payer before the primary processes the claim, outdated COB information in the payer's records (the patient acquired new primary coverage but the secondary was not updated), or Medicare Secondary Payer situations where employer-sponsored insurance should be billed first. The RARC MA04 frequently accompanies CARC 22, explicitly stating that secondary payment cannot be considered without primary payer payment information.

COB-related denials account for an estimated 15 to 20 percent of all claim denials industry-wide, and each reworked claim carries a cost of $25 to $50 in staff time and administrative overhead. The resolution is procedural rather than clinical: determine the correct COB order, submit to the primary payer, wait for their adjudication, and then forward the claim to the secondary payer with the primary's EOB. Preventing these denials requires consistent insurance verification workflows that capture all active policies — not just the card the patient presents — at every visit.

Common Causes

How to Resolve

Determine the correct primary/secondary payer order, submit to the primary payer first, then bill the secondary payer with the primary's EOB.

1. Identify the correct primary payer Contact the patient to verify all active insurance coverage. Use COB determination rules (Birthday Rule, employment status, MSP rules) to establish the correct payer order.
2. Submit to the primary payer File the claim with the correct primary insurer and wait for adjudication. Do not submit to the secondary until you have the primary's EOB.
3. Resubmit to the secondary with primary EOB After the primary processes the claim, send the secondary claim with the primary's EOB attached showing payment and adjustments.
4. Update COB records in your system and with the payer Correct the patient's COB information in your practice management system and notify the payer of the corrected COB order to prevent future CARC 22 denials.

Common RARC Pairings

The RARC code tells you exactly what triggered the CO-22:

How to Prevent CO-22

• Verify all active insurance policies at every patient visit — ask about spouse's employer coverage, Medicare, Medicaid, auto insurance, and any other active policies
• Use real-time electronic eligibility verification to confirm COB status and primary/secondary payer order before claim submission
• Train front-desk staff on COB determination rules including the Birthday Rule, employment status rules, and Medicare Secondary Payer rules
• Maintain COB questionnaires that patients complete at registration and update at least annually
• Use pre-submission claim scrubbers that validate COB information and flag potential COB issues before the claim is sent to the payer
• Always wait for primary payer adjudication before submitting secondary claims

General Prevention

• Verify all active insurance coverage at every patient visit, not just the insurance card presented, by asking about other policies including spouse's employer coverage, Medicare, Medicaid, and liability/auto insurance
• Use real-time electronic eligibility verification to confirm the patient's COB status and primary/secondary payer order before claim submission
• Train front-desk staff on COB determination rules including the Birthday Rule for dependents, employment status rules for retirees, and Medicare Secondary Payer rules
• Maintain and update patient COB questionnaires at registration and at least annually to capture coverage changes
• Use pre-submission claim scrubbers that validate COB information and flag potential COB issues before the claim is sent
• Always wait for primary payer adjudication before submitting secondary claims, and always attach the primary EOB to secondary submissions

Also Filed As

The same CARC 22 may appear with different Group Codes:

Related Denial Codes