CO-50 denial code
The payer does not consider the service medically necessary for the diagnosis you submitted. In Medicare, this almost always means the diagnosis is not on the covered list in the applicable coverage policy for your jurisdiction.
CO — Contractual Obligation. The write-off is yours. You agreed to it in your contract with the payer, and you cannot bill the patient for it.
Why you got it
- 1The diagnosis code does not appear in the covered list of the Local Coverage Determination or coverage article that governs the service.
- 2A more specific diagnosis exists in the chart that would have supported necessity, and an unspecified code was submitted instead.
- 3The diagnosis is genuinely not covered for this service, and the patient should have signed an ABN.
- 4The coverage policy changed and the claim was coded against the old one.
How do I fix a CO-50 denial?
- Read the actual coverage policy for your Medicare contractor. Coverage is jurisdictional — the same code can be covered in Texas and not in Ohio.
- If the documentation supports a diagnosis that IS on the covered list, recode and resubmit. If it does not, do not code one that is not supported.
- If an ABN was signed, bill the patient with the appropriate modifier. If it was not, the write-off is yours.
How to stop the next one
Medical necessity is knowable before submission. The coverage policy for your contractor is published, it is public, and it names the diagnoses it will accept.
We can catch the coding cause of this one before you submit
Paste the diagnosis codes into our free scrubber and it will flag the invalid, incomplete, and conflicting codes that produce CO-50 — quoting the CMS note behind each one. No signup.
Check a claim, freeIf denials like this are a volume problem rather than a one-off, the denial management page explains how the paid workspace catches the coding causes on every claim, and the free ICD-10-CM lookup shows the coding notes behind any diagnosis code on the remittance.