CO-22: May be covered by another payer

What causes CO-22?

• The patient has other coverage the practice did not know about
• The payer’s COB record is stale, often for months after a change
• Medicare Secondary Payer rules apply and were not identified
• A work injury or motor vehicle claim should be primary

How do you fix a CO-22 denial?

1. Call the patient before you call the payer. They can usually resolve the COB record themselves in one phone call, and the payer will not update it on your say-so
2. For Medicare, check the MSP record and identify which MSP category applies
3. Once COB is corrected, the claim usually needs resubmitting rather than reprocessing — ask which
4. Bill the correct primary first and attach the primary remittance when billing the secondary

Can CO-22 be prevented?

Eligibility checked before the visit catches most of these while the patient is still in front of you, which is the only cheap moment to catch them.

A denial like this one is the recurring cost that medical billing outsourcing is built to take off your desk — a dedicated seat working the queue instead of it waiting for whoever has a free hour.

Codes worked the same way

CO-22 is fixed at coordination of benefits and rebilled. So are these, which is why a queue sorted by recovery route moves faster than one sorted by code number — the same person, in the same system, with the same evidence to hand, clears all of them in one pass.

• CO-27 — Coverage had already ended
• CO-109 — Wrong payer or contractor
• CO-119 — Benefit maximum reached
• PR-31 — Patient not found as insured
• CO-24 — Covered under capitation
• CO-32 — Not an eligible dependent

Specialties that name this among their costliest

These are specialties whose own worst denials include one of this kind. The line under each is the denial they name, quoted from their page so you can see what the link is based on.

• Behavioral Health
  Add-on codes billed without the primary service
• Podiatry
  Orthotics denied for coverage exclusion
• Obstetrics & Gynecology
  Coverage checked once at the first prenatal visit and never rechecked, so the delivery claim months later goes to a plan the patient has already left.
• Urgent Care
  Coverage taken from whatever card the walk-in hands over at the desk and never checked against the plan, so the claim goes to a policy the patient left months ago
• Primary Care
  Low-dollar denials — the patient assigned to a different primary care provider, a wrong place of service — left in the queue as not worth the call, then aged past timely filing.
• Clinical Laboratory and Pathology
  Tests denied for a diagnosis not on the coverage policy's approved list

What leaving it costs

Working a denied claim costs $57.23 per denied claim in administrative time (source) — before any of it is recovered, and whether or not it ever is.

Payers ultimately pay roughly 90% of claims even while using an initial denial to slow payment (source), so the reason one sits is rarely that nobody knows how to work it. Put your own denial count in.

Questions

Code descriptions are the standard X12 claim adjustment reason and remittance advice remark code text. Payer policies differ, and the payer’s own coverage policy governs any individual claim. This page is working guidance, not legal or clinical advice.