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N456 Remark Code: Incomplete or Invalid Physician Order

N456 means the physician order was incomplete or invalid. An order was provided, but it lacked required elements, such as a signature, date, patient identification, or a clear description of what was ordered, or it did not match the service billed.

Code: N456 (RARC N456)
Status: Active In use since July 1, 2008.
Code set: Remittance Advice Remark Codes (RARC)
Group codes: CO (Contractual Obligation): The payer will not pay until a valid order is supplied. The provider obtains a compliant order; the patient is not billed.
Official description: Incomplete/invalid Physician Order.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What N456 means

N456 says the payer has an order, but it does not accept it. The document might be unsigned, undated, missing the patient’s identifying information, vague about what was ordered, or dated after the service. It also appears when the order describes something different from what was billed. Expect it with CARC 251 or with CARC 175 (prescription incomplete).

Order defects that commonly trigger N456

Authentication problems: missing or illegible signature, stamped signature, no practitioner credentials.
Date problems: undated order, or an order dated after the service when the payer requires it beforehand.
Content problems: item or test not specific enough, missing quantity, frequency, or length of need for equipment and supplies.
Mismatch: the order is for a different test, item, or body part than the claim.
Wrong practitioner: the ordering provider on the claim differs from the one who signed the order, or is not eligible to order.

How to fix it

Identify the defect, from the payer’s notice or by calling.
Contact the ordering practitioner for a corrected or complete order. Any correction should be properly dated and should not backdate the original.
Align the claim with the order. If the claim listed the wrong ordering provider or item, correct it and resubmit with resubmission code 7.
Send the valid order with the claim number on each page.

How to prevent it

Check each incoming order for the required elements before accepting it, and send back incomplete orders right away. For equipment suppliers and diagnostic providers, a standard order-intake checklist prevents most N456 denials.

Codes that may appear with N456

CO-251 (The attachment/other documentation that was received was incomplete or deficient.): The documentation received was incomplete or deficient.
CO-175 (Prescription is incomplete.): The prescription is incomplete.
CO-176 (Prescription is not current.): The prescription is not current.

N455 (Missing Physician Order.): No physician order was received.
N575 (Mismatch between the submitted ordering/referring provider name and the ordering/referring provider name stored in our records.): The ordering or referring provider name does not match the payer's records.
CO-184 (The prescribing/ordering provider is not eligible to prescribe/order the service billed.): The ordering provider is not eligible to order the service billed.

N456 FAQ

What does a valid order usually include?

The patient's name, the date of the order, a description of the item or service in enough detail, the ordering practitioner's name and signature, and for some items, quantity, frequency, or duration. Payers may require more.

Is a stamped signature acceptable?

Many payers, including Medicare, do not accept stamped signatures. Handwritten or compliant electronic signatures are the safe choice.

What if the order is for a slightly different item than billed?

The order should support exactly what was provided. If it doesn't, get a corrected order where appropriate, or bill what was actually ordered.

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