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N204 Remark Code: Pre-Existing Condition Review

N204 means the payer is reviewing whether the services relate to a pre-existing condition and wants medical records covering the prior 12 months before it decides. The claim is on hold or denied until those records arrive.

Quick facts

Code
N204 (RARC N204)
Status
Active In use since June 30, 2003.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The claim is held or denied pending records. The provider is expected to send them; the patient should not be billed while the review is open.
  • PR (Patient Responsibility): If the review concludes the condition is excluded under the plan, the amount may become patient responsibility, depending on plan terms.
Official description
Services under review for possible pre-existing condition. Send medical records for prior 12 months
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N204 means

N204 says the payer has not made a final decision. It wants to know whether the condition being treated existed before the patient’s coverage began, and it has asked for 12 months of prior medical records to decide. The remark usually appears with CARC 252 (documentation required) while the review is pending, or CARC 51 once the payer concludes the condition is excluded.

Pre-existing condition reviews are less common than they once were for comprehensive health plans, but they still appear with some limited or supplemental coverage and in certain other plan types.

Common causes

  • The patient’s coverage started recently and the diagnosis suggests a long-standing condition.
  • The plan is a type that still includes a pre-existing condition clause.
  • The diagnosis was reported without history, prompting the payer to check.

How to fix it

  1. Confirm what the payer wants: date range, record types, and where to send them.
  2. Collect records from the preceding 12 months, including visit notes, problem lists, and medication history.
  3. Send the records with a cover letter referencing the claim number, using the payer’s attachment channel.
  4. Follow up to confirm receipt, and track the review until a final decision.
  5. If the payer denies under a pre-existing clause you think does not apply, appeal with evidence of the onset date or the plan’s terms.

How to prevent it

Verify plan type at registration so staff know when pre-existing clauses may be in play, and respond quickly to records requests. Clear documentation of onset dates in the chart helps reviewers decide faster.

Codes that may appear with N204

  • CO-51 (These are non-covered services because this is a pre-existing condition.): Non-covered because this is a pre-existing condition, the likely outcome if the review goes against coverage.
  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): Documentation is required to adjudicate the claim; the prior records are that documentation.
  • CO-226 (Information requested from the Billing/Rendering Provider was not provided or not provided timely or was insufficient/incomplete.): Requested information from the provider was not received or was incomplete.
  • M127 (Missing patient medical record for this service.): Missing patient medical record for this service.
  • N237 (Incomplete/invalid patient medical record for this service.): The medical record sent was incomplete or invalid.

N204 FAQ

Do pre-existing condition exclusions still apply?

Many major medical plans no longer exclude pre-existing conditions under current federal law, but some plan types, such as certain short-term, supplemental, or excepted-benefit policies, may. The payer's plan type determines whether the review matters.

Which records should I send?

The remark asks for records from the prior 12 months. Send notes, diagnoses, and treatment history for that period from your practice and any records you hold from others.

What if the patient is new and we have no prior records?

Tell the payer that. The payer may seek records from other providers or from the patient.