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Denial Codes/CO-4
CO-4Contractual Adjustment

Missing or incorrect modifier

What this code means

Your claim was missing a code that tells the insurer more detail about how or where a service was performed. Without it, the claim cannot be processed.

What to do next

Ask your provider to review the claim for missing modifiers and resubmit with the correct modifier attached. This is a provider-side fix, not an appeal.

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Related denial codes

  • CO-11Diagnosis does not support the procedure
  • CO-15Prior authorization missing or invalid
  • CO-16Missing information or submission error
  • CO-18Duplicate claim
View all denial codes
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