CO 22 denial code

What CO-22 means

CO-22 means the payer believes another insurer should pay first. Its coordination of benefits (COB) records show other coverage: an employer plan, a spouse’s plan, workers’ compensation, auto liability, or Medicare Secondary Payer situations. As a result, it will not adjudicate as primary until payer order is resolved.

The CO group code means contractual obligation, so the denied amount is not billable to the patient. But CO-22 is not a true write-off situation: the money exists, it just lives with a different payer or is waiting on updated COB information.

The single most common pairing on Medicare remits is CO-22 with remark code MA04: the payer needs the primary payer’s identity or payment information before it can consider the claim as secondary. That pairing tells you exactly what to send.

Common causes

• Wrong payer billed first. The patient has employer coverage that is primary to Medicare (for example, a working beneficiary with a large-group health plan), and the claim went to Medicare first.
• Stale COB files. The payer’s records show a plan the patient dropped years ago. Nothing is wrong with your claim: the patient’s COB record is out of date.
• Missing primary payment data. A secondary claim submitted without the primary’s payment and adjustment details.
• Accident-related diagnoses. Injury codes trigger third-party liability logic: auto, liability, or workers’ compensation may be primary for those charges.
• Registration gaps. Other coverage that existed at check-in was never captured, so the claim was built with the wrong payer order.

How to fix and resubmit

1. Read the remark code. MA04 means the payer needs primary payer information; that is a resubmission fix, not a dispute.
2. Verify coverage yourself. Run eligibility on the payer that denied, and check what other coverage it has on file. For Medicare, the MSP record shows what Medicare believes is primary and why.
3. If another payer really is primary, bill that payer first, then submit to the denying payer as secondary with the primary’s remittance details attached. Watch each payer’s timely filing limit: filing to the wrong payer does not always protect the clock with the right one, so move fast.
4. If the “other coverage” is dead, the patient must contact the plan and update their COB; payers generally will not take that update from the provider. Give the patient the plan’s number, diarize the account for 2-4 weeks, then resubmit once the COB record is corrected.
5. If Medicare’s MSP record is wrong, the patient (or the office, with the patient) can contact the Benefits Coordination & Recovery Center to correct it, then resubmit.
6. Appeal only when you have evidence the denying payer genuinely is primary and its COB determination is wrong. Most CO-22s resolve through resubmission, not appeal.

How to prevent it

COB failures start at the front desk, so fix them there: ask every patient about other coverage at every visit (including spouse’s employer coverage, retiree plans, and recent job changes) and run eligibility checks that return COB data before the claim goes out. For Medicare patients, screen with the MSP questionnaire and record the answers. For injury visits, capture accident details at registration so liability claims route correctly from the start. Compare with CO-24, the related denial where a managed care plan holds the benefits, and see the denial codes index for more.