CO-22 denial code
This care may be covered by another payer per coordination of benefits
How to fix it
Confirm the correct payer order with the patient, bill the primary payer first, then submit to this payer with the primary's explanation of benefits.
How to prevent it
Capture and verify all active coverage at registration, including secondary and tertiary, and re-verify periodically.
In practice
A claim returns CO-22 — this care may be covered by another payer per coordination of benefits. The patient holds coverage through their own employer and is also a dependent on a spouse's plan, and the claim went to the wrong one first.
Coordination of benefits rules determine which plan pays first, and they are not a matter of patient preference. For dependent children, many plans apply the birthday rule — the plan of the parent whose birthday falls earlier in the calendar year is primary, regardless of which parent is older.
The fix is to establish the correct order, bill the primary payer, and then submit to the secondary with the primary's explanation of benefits attached. Filing deadlines run throughout, so time spent determining the order is time consumed from the secondary's window.
What sits behind it
CO-22 is an information failure at registration rather than a claim defect. The patient usually knows they have two coverages; nobody asked, or asked once at intake and never again.
Coverage changes constantly — employment, marriage, a spouse's open enrolment, a child ageing off a plan, Medicare eligibility. Verifying only at first visit means the record is accurate on day one and progressively less so afterwards.
Medicare secondary payer rules add a further layer, with defined circumstances in which Medicare is secondary to group health coverage. Those situations have their own questionnaire and their own documentation expectations, and getting the order wrong produces both a denial and a compliance exposure.
Related codes
Terms used here — Coordination of Benefits · Eligibility Verification · Timely Filing
How we handle it — Eligibility Verification · Claims Management · Denial Management
Primary sources
The rules behind CO-22, at the bodies that publish them.
- Medicare Secondary Payer Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — When Medicare pays second, and to whom the claim goes first. Coordination-of-benefits denials are resolved here rather than with the patient.
- Medicare Claims Processing Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — The operative manual for how Medicare claims must be coded, submitted, adjusted and appealed. When a payer policy and a vendor's advice disagree, this settles it.
Every denial code with a guide
Authorization
Bundling
Contractual
Coverage
Data quality
Documentation
Eligibility
Liability and workers comp
Patient responsibility
Provider eligibility
Timely filing
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-22
The payer believes another plan is primary for this care. It is a coordination of benefits issue rather than a coverage denial — the service may be perfectly covered, once billed to the correct payer in the correct order.
By coordination of benefits rules, not patient preference. Employer coverage is typically primary over a spouse's plan for the employee. For dependent children many plans apply the birthday rule — the parent whose birthday falls earlier in the calendar year is primary, regardless of age.
After the primary adjudicates, submit to the secondary with the primary's explanation of benefits attached. Secondary filing deadlines often run from the primary's remittance date rather than the date of service, so delays in resolving the order consume the secondary window.
Ask about all active coverage at every visit rather than only at intake. Coverage changes with employment, marriage, open enrolment and Medicare eligibility, so a record verified once is accurate on day one and progressively less so afterwards.
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