N657: Service billed with inappropriate modifier, or a required modifier is missing or invalid for this anatomical site
The modifier attached to this procedure code does not fit the service or anatomical site described, or a modifier that should have clarified the anatomical site or laterality was left off.
Corrective actions
- 1
Review the modifier against the clinical documentation
Confirm the correct anatomical or laterality modifier (such as RT, LT, or a global-period modifier) supported by the operative or clinical note.
- 2
Correct the modifier and resubmit
Remove or replace the incorrect modifier with the one supported by documentation and resubmit as a corrected claim.
Usually paired with
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.