CO-22 Denial Code: Coordination of Benefits

The official definition

“This care may be covered by another payer per coordination of benefits”

That is the verbatim definition of CARC 22 from the X12 Claim Adjustment Reason Code set, the standardized codes every insurer uses on EOBs and remittance advices. The letters in front of the number are the group code. CO: Contractual Obligation: an adjustment between the provider and the insurer. An in-network provider should not bill you for CO amounts.

What it means in plain English

The insurer believes you have other health insurance that should pay first: a spouse's plan, a parent's plan, Medicare. The treatment isn't being questioned at all; the billing order is. COB denials are almost always fixable, because the only thing wrong is which insurer got the claim first.

What to check on your EOB

• Whether you actually have other coverage. Insurers' COB records are often stale (an old employer plan that ended years ago is a common culprit).
• If you do have two plans: which one is primary under the COB rules (for kids on two parents' plans, the 'birthday rule' usually decides: the parent whose birthday falls earlier in the year is primary).
• Whether an unanswered COB questionnaire is sitting in your mail. Insurers routinely deny claims while waiting for one.

What to do next

1. If you have no other coverage: call the insurer, tell them their COB information is wrong, complete their questionnaire, and ask them to reprocess the claim.
2. If you do: make sure the provider bills the primary plan first, then submits the primary EOB to the secondary plan.
3. If other coverage recently ended, give the insurer the termination date and request reprocessing.

Who's responsible

You + provider. Most denials carry a clear owner. Knowing whether the fix belongs to you, your doctor, or the billing office is half the battle. If it's the provider's error, you should not be paying for it.

Want the fundamentals first? Start with how to read an EOB and the 7 most common billing errors. This page is general information about standardized denial codes, not legal or medical advice.