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N400 Remark Code: Submit Claims Electronically

N400 is an informational alert. The payer's records show you are able to submit claims electronically, and it is reminding you that you should do so instead of sending paper claims.

Code: N400 (RARC N400)
Status: Active In use since August 1, 2007.
Code set: Remittance Advice Remark Codes (RARC)
Group codes: CO (Contractual Obligation): Any adjustment on the claim follows your contract. The alert itself doesn't create a patient balance or a denial.
Official description: Alert: Electronically enabled providers should submit claims electronically.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified: September 24, 2026 against the official X12 list.

What N400 means

Paper claims cost payers more to handle and take longer to process. N400 is a nudge: the payer knows you’re capable of electronic submission and is asking you to use it. It doesn’t change the outcome of the current claim.

It can appear on any processed paper claim, alongside whatever CARC applies to the line.

What to do

Read the CARC for this claim’s actual result.
Find out why the claim went on paper. Was it a secondary claim, a claim with attachments, or a payer not set up in your clearinghouse?
Close the gap. Enroll the payer in your clearinghouse, set up electronic COB for secondary claims, and use electronic attachments where the payer supports them.
Check for mandates. Some payers and programs require electronic submission; repeated paper claims could eventually be rejected under those rules.

Electronic claims also get faster front-end edits, which helps you catch errors earlier. See claim rejection vs denial for how front-end rejections work.

Codes that may appear with N400

CO-45 (Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.): May appear on a processed paper claim with a routine fee schedule adjustment; the alert concerns the submission method only.

M117 (Not covered unless submitted via electronic claim.): A stronger rule: the service is not covered unless submitted via electronic claim.
N34 (Incorrect claim form/format for this service.): Says the claim form or format is incorrect for the service.
N51 (Electronic interchange agreement not on file for provider/submitter.): Says an electronic interchange agreement is not on file for the provider or submitter.

N400 FAQ

Was my paper claim denied?

Not because of N400. Check the CARC for the claim's result. The alert is a reminder about future submissions.

Could the payer start rejecting paper claims?

Some payers and programs require electronic submission unless an exception applies. Read your contract and the payer's billing rules.

What if I have a reason to bill on paper?

Some payers accept paper for specific situations, such as certain attachments or exception waivers. Ask the payer what exceptions it allows.

Important: read before using this information

This page is general educational information about a standard industry code set. It is not medical billing, coding, legal, reimbursement, or compliance advice, and it does not create a professional or advisory relationship with ClaimsRevenue.

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