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N451 Remark Code: Missing Admission Summary Report

N451 means the admission summary report is missing. The payer needs a document describing why and how the patient was admitted, and it did not receive one with the claim or in response to a request.

Quick facts

Code
N451 (RARC N451)
Status
Active In use since July 1, 2008.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The claim is denied or pended until the report is received. The facility or provider supplies it; the patient is not billed.
Official description
Missing Admission Summary Report.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N451 means

An admission summary report captures the start of a stay: why the patient came in, what the admitting provider found, and the initial plan of care. Payers use it to confirm that an admission was appropriate and, in injury cases, that it relates to the condition being claimed. N451 tells you the payer needed that report and does not have it.

It is typically paired with CARC 252 (documentation required) or CARC 226 (requested information not provided).

What the payer is looking for

The document usually needs to show:

  • the reason for admission and the presenting condition,
  • the admitting provider’s findings and working diagnosis,
  • the initial treatment plan and level of care, and
  • the admission date, matching the claim.

A facility’s admission history and physical often covers these elements, but some payers and jurisdictions specify their own format.

How to fix it

  1. Check for a records request. The payer may have asked for the report earlier; find the request and its deadline.
  2. Pull the admission documentation from the medical record, signed and dated.
  3. Label it clearly with the patient name, claim number, and dates of the stay.
  4. Send it through the payer’s attachment channel, electronic or paper, and keep proof of submission.
  5. Follow up to confirm the payer received and matched it to the claim, then ask for reprocessing.

How to prevent it

For payers or claim types that routinely request admission documentation, attach the admission summary when the claim goes out. Route records requests to a single queue with deadlines so they are not missed. Background on attachment-related codes is in how CARC and RARC codes work.

Codes that may appear with N451

  • CO-252 (An attachment/other documentation is required to adjudicate this claim/service.): An attachment or other documentation is required; N451 names the admission summary report.
  • CO-226 (Information requested from the Billing/Rendering Provider was not provided or not provided timely or was insufficient/incomplete.): Information requested from the billing or rendering provider was not provided or was insufficient.
  • CO-163 (Attachment/other documentation referenced on the claim was not received.): An attachment referenced on the claim was not received.
  • N452 (Incomplete/invalid Admission Summary Report.): The admission summary report was received but was incomplete or invalid.
  • N459 (Missing Discharge Summary.): The discharge summary, the report at the other end of the stay, is missing.
  • M127 (Missing patient medical record for this service.): The patient's medical record for the service is missing.

N451 FAQ

Is an admission summary the same as the history and physical?

They overlap. Many facilities use the admission history and physical as the admission summary. Ask the payer whether it will accept that document or wants a specific form.

Which claims are most likely to need it?

Inpatient and other facility admissions under review, and workers' compensation or other property and casualty claims where the carrier needs to link the admission to the injury.

What if we already sent the full chart?

Point the payer to where the admission summary sits in what you sent, or resend it separately and clearly labeled, since reviewers may not find it in a large record.