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- The payer's COB file is out of date.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. Payer-by-payer: fixing CO-22
| Payer | What to know |
|---|---|
| Medicare | Medicare's Secondary Payer (MSP) record drives CO-22. If the record is wrong, the beneficiary or provider contacts the Benefits Coordination & Recovery Center (BCRC) to update it, then the claim can be resubmitted. Check MSP data in your eligibility response before rebilling. |
| Medicare Advantage | The MA plan manages its own COB file, not the BCRC. Call the plan's provider line or have the member update other coverage with the plan. |
| Medicaid | Medicaid is the payer of last resort. Bill every other coverage first and send the primary's remittance with the Medicaid claim. If the state's third-party liability (TPL) file shows coverage that has ended, the state TPL unit corrects it. |
| Commercial plans | Many plans send members a COB questionnaire and pend or deny claims until it comes back. The fastest fix is usually the member calling the plan or updating coverage in the member portal, then asking for reprocessing. |
| TRICARE | TRICARE pays after almost all other health coverage, except Medicaid and a few federal programs. Bill the other plan first. |
Whatever the payer, note the date the COB record was corrected and the reference number. Payers reprocess faster when you can quote both.
6. 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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