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N597 Remark Code: Apportioned to Unrelated Conditions

N597 means the payer adjusted payment based on a medical or dental provider's apportionment of care between the related injury and other, unrelated conditions or injuries. Only the share attributed to the covered injury is paid.

Quick facts

Code
N597 (RARC N597)
Status
Active In use since July 15, 2013; last modified November 1, 2013.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The apportioned amount is adjusted off this claim. The unrelated share may be billable to other coverage.
  • OA (Other Adjustment): Some carriers use OA to signal that another payer should consider the unrelated portion.
Official description
Adjusted based on a medical/dental provider's apportionment of care between related injuries and other unrelated medical/dental conditions/injuries.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N597 means

When a patient has both a covered injury and other conditions, such as prior degenerative changes, a clinician may be asked to estimate how much of the treatment relates to each. That split is called apportionment. N597 says the payer used such an estimate to reduce your payment to the share it considers related.

This is mostly a workers’ compensation and injury-claim concept. It typically appears with CARC P32 (apportionment) or CARC 219 (extent of injury).

Common causes

  • A pre-existing condition in the same body area.
  • Multiple injuries from different incidents being treated together.
  • An IME or reviewer assigned part of the care to non-work or non-accident causes.

What to do

  1. Get the apportionment opinion the payer relied on and its percentage or basis.
  2. Review your documentation on causation and whether the treatment targeted the injury.
  3. Dispute with a supporting opinion from the treating provider if you disagree, within the jurisdiction’s deadlines.
  4. Bill the unrelated share to the patient’s other coverage when appropriate.

How to prevent problems

Document clearly which conditions each service treats and link diagnoses to the accepted injury. When treating both related and unrelated problems at a visit, keep the services and diagnoses distinct so apportionment is less likely to be applied across the board.

Codes that may appear with N597

  • CO-P32 (Payment adjusted due to Apportionment.): Payment adjusted due to apportionment.
  • CO-219 (Based on extent of injury.): Based on extent of injury.
  • N576 (Services not related to the specific incident/claim/accident/loss being reported.): Services are not related to the reported incident at all.
  • N607 (Service provided for non-compensable condition(s).): The service was provided for non-compensable conditions.
  • N591 (Payment based on an Independent Medical Examination (IME) or Utilization Review (UR).): Payment was based on an IME or utilization review.

N597 FAQ

Who decides apportionment?

A treating or examining medical or dental provider gives an opinion on how much of the care relates to the injury. The payer applies it, often under workers' compensation rules.

Can I bill the unrelated share elsewhere?

Possibly, to the patient's health insurance. That plan may need the injury payer's remittance and may have its own rules.

How do I dispute an apportionment?

Through the payer's reconsideration process or the state's dispute process, with a supporting medical opinion.