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N322 Remark Code: Last Certification Date Invalid

N322 means the last certification date was missing, incomplete, or invalid. For services that require periodic certification or recertification, the payer needs the date of the most recent one to confirm the service was covered by it.

Quick facts

Code
N322 (RARC N322)
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 certification date; the adjustment is not patient responsibility.
Official description
Missing/incomplete/invalid last certification date.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N322 means

Ongoing services like outpatient therapy, home health, and some rented equipment are covered only while a current certification is in place. Each time the certification is renewed, a new date is created. Payers compare that most recent date with the dates of service to confirm coverage. N322 tells you the date was absent or couldn’t be used.

It generally comes with CARC 16; if the payer also wants to see the certification, CARC 252 may be added.

Common causes

  • The initial certification date was sent instead of the most recent recertification.
  • The recertification was signed, but the date was never entered in the billing system.
  • The certification date is after the date of service, suggesting the service was provided before it was certified.
  • Several certifications exist, and the wrong one was matched to this billing period.
  • The date format or value is invalid.

What to do

  1. Pull the full certification history for the patient and service.
  2. Identify which certification covers the dates of service on the claim.
  3. Confirm it was signed and dated in line with the payer’s timing rules.
  4. Enter the correct date in the claim field the payer uses for it.
  5. Resubmit with frequency code 7, and send the certification if the payer requests it.

How to prevent it

Track certification dates as events with due dates for the next recertification. A work queue that shows patients approaching expiration helps clinicians get signatures on time. On the billing side, link each claim to the certification that covers it so the date is never re-keyed. Units and frequency limits often come up at the same time; see our MUE guide.

Codes that may appear with N322

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Missing or invalid information; N322 names the last certification date.
  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): Documentation, such as the certification itself, is required.
  • N313 (Missing/incomplete/invalid certification revision date.): The certification revision date is missing or invalid.
  • N486 (Incomplete/invalid Physical Therapy Certification.): The physical therapy certification is incomplete or invalid.
  • N320 (Missing/incomplete/invalid Home Health Certification Period.): The home health certification period is missing or invalid.

N322 FAQ

What is a 'last certification date'?

The date of the most recent certification or recertification covering the service, such as a signed therapy plan of care or a renewed DME certification.

What if recertification is overdue?

The service may not be covered until a valid recertification is obtained. Changing the date on the claim won't solve a missing recertification.

Where does the date go?

That depends on the claim type and payer. Institutional therapy claims and DME claims each have their own conventions; follow the companion guide.