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.
Denial codes it is usually paired with
N657 is the detail behind a CARC rather than an adjustment in its own right. These are the denial codes our dataset records it alongside.
Frequently asked questions
What does remark code N657 mean?
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.
Retrieved 2026-07-18.
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Denial7 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.