How to fix a CO-22 denial
Find the primary payer, bill it first, then bill this one as secondary.
CO-22 means the payer believes another plan should pay first under coordination of benefits. Confirm the order of coverage, bill the primary payer, then send this payer a secondary claim with the primary’s payment details.
- Meaning
- Another payer may pay first
- Group code
- CO: not a patient balance
- Usual fix
- Bill the primary, then rebill
- Prevent it
- Ask about other coverage
What the CO-22 denial code means
Claim adjustment reason code 22 reads, in the official X12 list, "This care may be covered by another payer per coordination of benefits." In plain terms, the payer’s records show other coverage that should pay before it does, so it has denied the claim or the line until that coverage is billed or ruled out.
The CO group code means contractual obligation: the adjustment comes from your payer contract or a regulation, not from the patient’s share. The Medicare Claims Processing Manual describes CO amounts as generally a write-off for the provider, not billed to the patient. With CO-22 the balance is not a write-off yet: the payer is pointing you to another plan, and the claim can be paid once the order of coverage is right.
Check the remark code beside it. MA04 says secondary payment needs the primary payer’s identity or payment details; N479 says the other payer’s explanation of benefits is missing. If the reason code is 19, 20 or 21 instead, the payer is pointing at workers’ compensation, a liability carrier or no-fault insurance.
Our guide to reading denial codes explains how the group, reason and remark codes fit together.
Common causes of CO-22 and how to fix each
Work out which one it is before you rebill. Each has a different fix.
- Other coverage nobody recordedAsk the patient, check the eligibility response for other insurance, bill the primary plan, then send this payer a secondary claim with the primary’s payment.
- Medicare should be secondaryAn employer group plan pays first for many working patients 65 and over, disabled patients and patients with ESRD. Bill that plan first.
- The other coverage has endedGet the end date, ask the payer to update its records and resubmit. For Medicare, ask your MAC to end the MSP record.
- A child covered by both parentsUnder the birthday rule, the plan of the parent whose birthday comes first in the year pays first.
- An accident, work injury or lawsuitWorkers’ compensation, no-fault or liability insurance pays first for the related care. Get the carrier, claim number and date of injury.
- A Medicaid patient with other insuranceMedicaid pays after other coverage. Bill the other plan first, then send Medicaid the claim with that plan’s payment or denial.
- The primary already paidThis payer did not get the primary’s payment details. Resend it as a secondary claim with the paid amounts and adjustments.
When Medicare pays second
Medicare calls this Medicare Secondary Payer (MSP), and the duty sits with you. Under Chapter 3 of the MSP Manual, providers, physicians and suppliers that bill Medicare must find out whether Medicare is primary by asking the patient about other coverage before the claim goes out. CMS publishes model intake questions for this.
The common cases, from the CMS Medicare Secondary Payer page:
- Age 65 or over, covered through their own or a spouse’s current job, employer of 20 or more employees: the group plan pays first
- Disabled, covered through their own or a family member’s current job, employer of 100 or more employees: the group plan pays first
- End-stage renal disease with a group plan or COBRA: that plan pays first during the 30-month coordination period
- An accident or a work injury: no-fault, liability or workers’ compensation pays first for the related care
Retiree plans, and COBRA outside the ESRD coordination period, pay after Medicare. When Medicare’s file shows coverage that has ended, such as after a retirement, your MAC can terminate the record; records you believe are invalid go to the Benefits Coordination & Recovery Center (BCRC) for investigation and deletion.
Two commercial plans, or Medicaid and another plan
Between two commercial plans, state insurance rules and the plans’ terms set the order. The NAIC Coordination of Benefits Model Regulation, written for state insurance commissioners to adopt, puts the plan that covers the patient as an employee, member or subscriber ahead of a plan that covers them as a dependent, and a plan covering an active employee ahead of one covering a retiree or laid-off employee.
For children of parents who are married or living together, the model uses the birthday rule: the plan of the parent whose birthday falls earlier in the calendar year is primary, and if both share a birthday, the plan that has covered a parent longer. For divorced or separated parents, a court decree comes first, then the custodial parent’s plan.
Medicaid normally pays after other coverage. Under 42 CFR 433.139, a state Medicaid agency that knows of other coverage when a claim is filed must reject the claim and return it so the other payer’s share can be settled first, with exceptions such as certain preventive pediatric services.
How we work a CO-22 denial
Read the line and the remark
We check whether the payer wants the other plan billed or only its payment details.
Confirm the order of coverage
We compare the eligibility response, the payer portal and the patient’s answers, and call the other plan if they disagree.
Fix the records
Coverage dates are corrected in your system, and stale records are updated with the payer, the MAC or the BCRC.
Bill in the right order
The primary payer gets the claim first; the secondary gets it with the primary’s payment and adjustments.
Watch the filing limits
Filing clocks keep running, so the secondary claim goes out as soon as the primary pays.
Close the gap at intake
If the same gap keeps causing CO-22, we change the intake step with your front desk.
Stopping CO-22 at check-in
The answer is often something the patient already knows: a spouse’s plan, a new job, a retirement or an accident claim. Our eligibility and benefits verification checks for other coverage and Medicare Secondary Payer records on every scheduled patient, and the steps below keep it from slipping:
- Ask about other coverage at each visit, not only at registration, and record the answer with the date
- Read the other-insurance and MSP sections of the eligibility response before the claim goes out
- Mark item 11d of the CMS-1500, or its electronic equivalent, and fill in the other insured’s details when a second plan exists, as the NUCC instructions require
- Get the carrier, claim number and date of injury from accident and work-injury patients
- Check coverage again in January and whenever a patient mentions a new job, a marriage or a retirement
It means the payer believes another plan should pay before it does under coordination of benefits. The CO group code puts the adjustment under your contract rather than on the patient. The fix is to confirm which plan is primary, bill that plan first, then send this payer a secondary claim with the primary’s payment.
Not while the amount carries group code CO. For Medicare, CMS says patients may be billed only for amounts under group code PR. The balance belongs with the primary payer, so get the other plan’s details from the patient and bill it. If that coverage has ended, get the end date and have the payer update its records before you resubmit.
Check the Medicare Secondary Payer record in the eligibility response. If an employer plan, an auto insurer or workers’ compensation is primary, bill it first, then send Medicare the claim with the primary’s payment. If the record is out of date, ask your MAC to end it. Move quickly: under 42 CFR 424.44, the 12-month filing limit runs from the date of service.
It decides which parent’s plan pays first for a child covered by both. Under the NAIC model regulation, when the parents are married or living together, the plan of the parent whose birthday falls earlier in the calendar year is primary. The year of birth does not matter. If both share a birthday, the plan that has covered a parent longer pays first.
No. CO-22 says another payer may be primary, so this payer may still pay as secondary once the primary has paid. Reason code 109 says the claim or service is not covered by this payer or contractor at all and must be sent to the correct payer or contractor. With 109, look for the right plan; with 22, bill in the right order.
Yes, when the payer’s coordination of benefits record is wrong and you have proof, such as a letter showing the other coverage ended. The faster route is often to have the payer correct its record and resubmit, and to appeal only if it will not. Our denial management team works both and tracks each against the payer’s deadline.
Yes. We don’t list our clients on this site, but ask us and we’ll arrange it: with a current client’s permission, we share their contact details so you can hear how we work from them directly.
Send us your CO-22 denials.
We’ll find the payer that should have been billed first, rebill in the right order and show you where intake missed it, free.