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N337 Remark Code: Secondary Diagnosis Date Invalid

N337 means a date associated with a secondary diagnosis on the claim, such as its onset or diagnosis date, was missing, incomplete, or invalid, and the payer needed it to process the claim.

Quick facts

Code
N337 (RARC N337)
Status
Active In use since December 2, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The claim was denied for a correctable data problem with a secondary diagnosis date. The patient is not billed for this adjustment.
Official description
Missing/incomplete/invalid secondary diagnosis date.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N337 means

Most claims send diagnosis codes without dates. A smaller set of payers and programs, however, want to know when a particular condition began or was diagnosed, and some apply that request to the secondary diagnoses on the claim, not just the principal one. N337 tells you a date linked to a secondary diagnosis was absent, incomplete, or inconsistent.

It usually comes with CARC 16. If the date problem makes a diagnosis look invalid for the service period, CARC 146 can appear.

Common causes

  • The payer or program requires onset dates for listed conditions, and only the principal diagnosis had one.
  • A date carried over from an earlier encounter falls after the current date of service.
  • The date was keyed in an unexpected format or without a year.
  • Diagnoses were re-sequenced during coding and the dates no longer line up with the right conditions.
  • Workers’ compensation, accident, or pre-existing condition reviews asked for dates the claim did not include.

What to do

  1. Read the payer’s remark in context to confirm which diagnosis the date problem applies to. The service line or claim-level position on the remittance can help.
  2. Check the medical record for the documented onset or diagnosis date of that condition.
  3. Verify that the date is before or on the service date and uses the payer’s format.
  4. Correct the claim and resubmit with frequency code 7 and the original claim number, or follow the payer’s reconsideration process if it asks for records instead.
  5. If you believe no date is required for that diagnosis, call the payer and ask which edit fired before resubmitting.

How to prevent it

For payers or programs that require condition dates, add those dates to your charge capture workflow so coders enter them while reviewing the note. Re-check dates any time diagnoses are re-ordered, and keep a list of which payers expect dates on secondary diagnoses.

Codes that may appear with N337

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Information is missing or invalid; N337 points to the date linked to a secondary diagnosis.
  • CO-146 (Diagnosis was invalid for the date(s) of service reported.): The diagnosis was invalid for the dates of service, a related problem that date errors can trigger.
  • N314 (Missing/incomplete/invalid diagnosis date.): Used when the diagnosis date in general is missing or invalid, rather than one tied to a secondary diagnosis.
  • M76 (Missing/incomplete/invalid diagnosis or condition.): Covers a missing or invalid diagnosis or condition, not its date.
  • N306 (Missing/incomplete/invalid acute manifestation date.): Addresses the acute manifestation date.

N337 FAQ

Why would a payer need a date for a secondary diagnosis?

Some payers use onset or diagnosis dates to decide whether a condition existed before coverage, whether it is related to an accident or work injury, or whether it fits a program's rules.

Is N337 about the diagnosis code itself?

No. The diagnosis code may be fine. N337 is about the date the payer expected alongside it.

Where is the date reported?

That depends on the claim type and payer. Institutional claims may use occurrence codes, and professional claims may use a date field or supplemental information. Check the payer's companion guide.