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N339 Remark Code: Similar Illness or Symptom Date Error

N339 means the date the patient first had the same or a similar illness or symptom was missing, incomplete, or invalid. Payers use it to judge whether a condition is new, recurring, or pre-existing.

Quick facts

Code
N339 (RARC N339)
Status
Active In use since December 2, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The claim was denied because the similar illness date could not be used. The provider corrects the claim; the patient is not billed for this adjustment.
Official description
Missing/incomplete/invalid similar illness or symptom date.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N339 means

A few payers ask not just when the current problem started but whether the patient had the same or a similar illness before, and if so, when. The answer helps them sort out pre-existing condition questions, recurring injuries, and accident liability. N339 tells you that date was expected and was missing, incomplete, or unusable.

It usually explains CARC 16. On plans with pre-existing condition provisions, the date may later support or rule out CARC 51.

Common causes

  • The payer requires a similar illness date for this service type, and the office did not know to send it.
  • The current illness onset date was placed in the similar illness field, or vice versa.
  • Box 15 was used for another date without the right qualifier, so the payer read it as the wrong kind of date.
  • The date is after the date of service or otherwise illogical.

How to fix it

  1. Ask the provider to confirm, from the history, whether the patient had the same or a similar condition before and when it began.
  2. Check the payer’s instructions for how to report it: which field, which qualifier, and what to send if there was no prior episode.
  3. Keep the current illness date (box 14) and the similar illness date separate so each lands in the right place.
  4. Submit a corrected claim with resubmission code 7 in box 22 and the original claim number.
  5. If the payer is using the date for a pre-existing condition review, have documentation ready in case it requests records.

How to prevent it

Include a prior episode question in the history template for services where payers ask for this date, such as spinal manipulation or injury-related care. Map each date to its own field and qualifier in your billing system so they are not overwritten.

Codes that may appear with N339

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): The claim is missing information; N339 names the similar illness or symptom date.
  • CO-51 (These are non-covered services because this is a pre-existing condition.): Services are not covered as a pre-existing condition, a decision this date can feed into.
  • N306 (Missing/incomplete/invalid acute manifestation date.): Covers the acute manifestation date, a related clinical date.
  • N314 (Missing/incomplete/invalid diagnosis date.): Used when a general diagnosis date is missing or invalid.
  • MA122 (Missing/incomplete/invalid initial treatment date.): Addresses a missing or invalid initial treatment date.

N339 FAQ

Where does the similar illness date go on a CMS-1500?

Older versions of the form had a dedicated box 15 for a same or similar illness. The current form labels box 15 'Other Date' and uses a qualifier to say which date it is, so check the payer's instructions for the qualifier it expects.

Do all payers need this date?

No. It is mostly requested for chiropractic, accident, and pre-existing condition reviews, and requirements vary by payer.

What if the patient never had a similar illness?

Then there is no date to report. If the payer still asks, call to confirm what it wants and whether a note in the additional information field is acceptable.