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N455 Remark Code: Missing Physician Order

N455 means the physician order is missing. The service or item billed must be ordered by a physician or other qualified practitioner, and the payer did not receive the order supporting it.

Quick facts

Code
N455 (RARC N455)
Status
Active In use since July 1, 2008.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The service is not payable without a valid order on file. The provider obtains and submits it; the patient is not billed.
Official description
Missing Physician Order.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N455 means

Many services are ordered rather than self-initiated: a lab test, an imaging study, a wheelchair, home health visits, therapy. The provider who performs or supplies them is not the one who decided they were needed. Payers want to see the order from the treating practitioner who did decide. N455 says that order was not provided.

N455 is usually paired with CARC 252 (documentation required), and sometimes with CARC 173 or 174 when the payer treats the missing order as a failure to prescribe.

Who holds the order

This is often the hard part. The order lives in the ordering provider’s chart, but the claim comes from a lab, imaging center, supplier, or agency. Common gaps include:

  • verbal or phone orders that were never documented and signed,
  • orders sent by fax that were not saved to the patient’s account,
  • standing orders that expired, and
  • electronic orders that stayed in the ordering practice’s system.

How to fix it

  1. Find out what the payer needs: a copy of the order, a specific form, or both.
  2. Request the order from the ordering practitioner if you do not have it, and make sure it is signed and dated.
  3. Check timing. Confirm the order date is on or before the date of service where the payer requires that.
  4. Submit the order through the payer’s attachment process, labeled with the claim number.
  5. Confirm the ordering provider is on the claim (box 17 and 17b on the CMS-1500) and correct the claim with resubmission code 7 if not.

How to prevent it

Do not schedule or deliver an ordered service without a signed order in hand. Scan every order into the patient account at intake, and set expiration reminders for standing orders.

Codes that may appear with N455

  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): Documentation is required; N455 names the physician order.
  • CO-173 (Service/equipment was not prescribed by a physician.): The service or equipment was not prescribed by a physician.
  • CO-174 (Service was not prescribed prior to delivery.): The service was not prescribed before delivery.
  • N456 (Incomplete/invalid Physician Order.): The physician order was received but was incomplete or invalid.
  • N265 (Missing/incomplete/invalid ordering provider primary identifier.): The ordering provider's primary identifier is missing or invalid on the claim.
  • N264 (Missing/incomplete/invalid ordering provider name.): The ordering provider's name is missing or invalid.

N455 FAQ

Which services typically require an order?

Diagnostic tests such as lab and imaging, durable medical equipment and supplies, home health, therapy, and many outpatient hospital services. Payer requirements vary.

Can the order be obtained after the service?

For many items, especially equipment and certain tests, the order must exist before the service. A late order may not satisfy the payer. Check the specific rule.

Does the ordering provider need to be on the claim too?

Often, yes. The ordering provider's name goes in CMS-1500 box 17 with the appropriate qualifier and the NPI in 17b.