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N324 Remark Code: Last Seen or Visit Date Invalid

N324 means the date the patient was last seen or visited was missing, incomplete, or invalid. Some payers require it to confirm that a physician has recently seen the patient, for example for routine foot care tied to a systemic condition.

Quick facts

Code
N324 (RARC N324)
Status
Active In use since December 2, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The provider must correct the date and resubmit; the patient is not responsible while the claim is correctable.
Official description
Missing/incomplete/invalid last seen/visit date.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N324 means

For some services, coverage depends on the patient being under active care from another clinician. Routine foot care is the familiar example: when it is covered because of a systemic condition like diabetes, payers may want to know when the patient last saw the physician managing that condition. N324 says that date was missing or couldn’t be accepted.

It is normally paired with CARC 16.

Common causes

  • The podiatry or specialist claim was sent without the date the patient was last seen by the managing physician.
  • The practice reported its own last visit date rather than the managing physician’s.
  • The date is later than the date of service, or outside the payer’s allowed window.
  • The date was placed in box 15 with the wrong qualifier, or in box 19 when the payer wanted another location (or vice versa).
  • The attending physician’s NPI was omitted alongside the date.

What to do

  1. Ask the patient or check records from the managing physician for the date of the last visit.
  2. Confirm it falls within the payer’s required window before the date of service.
  3. Report the date, and the managing physician’s NPI if required, where the payer instructs.
  4. Resubmit a corrected claim with frequency code 7 in box 22.

If the patient hasn’t seen the managing physician within the required time, the service may not qualify. Correcting the date alone won’t change that.

How to prevent it

For services that depend on a recent visit elsewhere, collect the date and physician at check-in, and verify it against outside records when possible. Store both in structured fields so they flow into the claim. A pre-billing edit that flags a missing or too-old last-seen date will keep these claims from going out incomplete.

Codes that may appear with N324

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Missing or invalid information; N324 names the last seen or visit date.
  • N323 (Missing/incomplete/invalid last contact date.): The last contact date is missing or invalid.
  • N335 (Missing/incomplete/invalid referral date.): The referral date is missing or invalid.
  • N334 (Missing/incomplete/invalid re-evaluation date.): The re-evaluation date is missing or invalid.

N324 FAQ

Where does the last seen date go on a CMS-1500?

Box 15 has a qualifier for the latest visit or consultation date. For routine foot care, Medicare instructs providers to report the date last seen and the NPI of the attending physician, commonly in box 19. Check each payer's instructions.

Whose visit counts?

Usually a visit with the physician managing the systemic condition, not the podiatrist's own previous visit. Payer rules define this.

Is there a time limit?

Some payers require the visit to be within a certain period before the service. The window varies, so check the payer's policy.