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N323 Remark Code: Last Contact Date Invalid

N323 means the last contact date was missing, incomplete, or invalid. The payer wanted the date of the most recent contact relevant to the claim, and what was reported could not be accepted.

Quick facts

Code
N323 (RARC N323)
Status
Active In use since December 2, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): A provider-correctable date problem; the patient is not billed for this adjustment.
Official description
Missing/incomplete/invalid last contact date.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N323 means

N323 is one of several date-specific remarks. It tells you the payer requires a “last contact” date and found it missing or unusable. Because the remark doesn’t define “contact” itself, the meaning comes from the payer’s rules. In practice it usually relates to services that depend on ongoing contact with the patient, such as care management, monitoring, or services where the time since the last interaction affects eligibility.

It usually appears with CARC 16.

Figuring out what the payer wants

The most useful first step is reading the payer’s documentation, because the fix depends on its definition. Ask:

  • Does the payer mean the last face-to-face visit, or any documented interaction?
  • Is the date related to a specific clinician, such as the physician who ordered the service?
  • Does the date need to fall within a set window before the service billed?
  • Which claim field does the payer use for it?

Common causes

  • The payer’s contact-date requirement was never configured, so the field is blank.
  • The date entered is later than the date of service.
  • A date from an unrelated encounter was used.
  • The format is invalid.

How to fix it

  1. Confirm the payer’s definition and required field.
  2. Check the record for the qualifying most recent contact before the service date.
  3. Enter the date in the correct field.
  4. Resubmit with frequency code 7 and the original claim number.
  5. If the definition is unclear, call provider services before rebilling.

How to prevent it

Once you know which payers and services require a last contact date, add it as a payer-specific claim rule and map it from a structured source, such as the encounter history or care management log. Reviewing remittances by remark, as shown in our CARC and RARC guide, helps you find where the requirement appears.

Codes that may appear with N323

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Missing or invalid information; N323 names the last contact date.
  • N324 (Missing/incomplete/invalid last seen/visit date.): The last seen or visit date is missing or invalid.
  • N334 (Missing/incomplete/invalid re-evaluation date.): The re-evaluation date is missing or invalid.
  • N309 (Missing/incomplete/invalid assessment date.): The assessment date is missing or invalid.

N323 FAQ

What counts as a 'contact'?

It depends on the payer and program. It can mean the last visit, a phone or telehealth interaction, or a care management contact. The payer's instructions define it.

Is N323 common?

It is uncommon on routine claims. It usually comes from payers or programs with specific contact-based requirements.

How is it different from N324?

N324 refers specifically to the date the patient was last seen or visited. N323 is broader and depends on how the payer defines contact.