CO-183: The referring provider is not eligible to refer the service billed.
The provider listed as making the referral is not recognized or eligible to authorize referrals for this type of service under the payer's rules.
What the group code means
- CO
- Contractual Obligation. The provider is responsible and the amount cannot be billed to the patient.
Why it fires
- The referring provider is not enrolled or credentialed with the payer
- The referring provider's specialty is not permitted to refer for this specific service type
- The wrong referring provider NPI was entered on the claim
Corrective actions, ranked
- 1
Verify the referring provider's enrollment
Confirm the referring provider is actively enrolled and eligible with this specific payer.
- 2
Correct the referring provider
If the wrong NPI was entered, correct it to the actual ordering or referring provider and resubmit.
- 3
Obtain a qualifying referral
If the original referring provider genuinely is not eligible, get a new referral from an eligible provider before resubmitting.
Is it worth appealing
Appeal only if the referring provider is in fact properly enrolled and eligible but the payer's data is out of date. Otherwise a new valid referral is needed.
Retrieved 2026-07-18.
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DenialPath provides billing and administrative guidance based on published CMS and X12 sources. It is not medical advice, not a coverage determination, and not a guarantee of payment. NCCI and MUE edits are republished quarterly and payer policies vary by contract. Always confirm against the payer's own current policy before submitting or appealing.