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N373 Remark Code: Refund to Wrong Primary Payer

N373 means the payer found that another payer paid your claim as primary even though it was not the primary payer. This payer is now refunding the payer that paid as primary on your behalf.

Quick facts

Code
N373 (RARC N373)
Status
Active In use since December 1, 2006.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • OA (Other Adjustment): The refunded amount is typically shown as an other adjustment because it moves money between payers rather than creating a patient or provider liability.
  • CO (Contractual Obligation): Some payers show the refund offset under CO. Reconcile it against the other payer's recoupment rather than writing it off blindly.
Official description
It has been determined that another payer paid the services as primary when they were not the primary payer. Therefore, we are refunding to the payer that paid as primary on your behalf.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N373 means

Coordination of benefits (COB) mistakes happen: the patient’s plans are billed in the wrong order, and the wrong plan pays first. N373 shows up when the correct primary payer discovers that. Instead of making you refund the other payer and rebill, this payer refunds the payer that paid as primary on your behalf and settles its own responsibility on this claim.

It’s typically paired with CARC 195, which explains the refund to an erroneous priority payer, and sometimes CARC 23.

Common causes

  • The patient’s other coverage wasn’t known when the claim was first billed.
  • Order-of-benefits rules (such as the birthday rule, active employee versus retiree, or Medicare secondary payer rules) were applied incorrectly.
  • A plan terminated or changed without the practice being told.
  • Enrollment records at one of the payers were outdated.

What to do

  1. Post the remittance and note the amount refunded to the other payer.
  2. Watch for the other payer’s remittance showing its reversal or recoupment, and match the two so the balance nets correctly.
  3. Update the patient’s insurance order in your system so future claims go to the correct primary.
  4. Check whether the former “primary” should now be billed as secondary, with this payer’s COB information.
  5. Contact both payers if the amounts don’t reconcile.

For the root causes of order-of-benefits errors, see eligibility and COB denials.

How to prevent it

Ask about other coverage at every visit, verify it with both payers, and record who is primary with the reason. Revisit the order when patients report job changes, marriage, Medicare enrollment, or a new plan year.

Codes that may appear with N373

  • CO-195 (Refund issued to an erroneous priority payer for this claim/service.): Refund issued to an erroneous priority payer for this claim or service.
  • OA-23 (The impact of prior payer(s) adjudication including payments and/or adjustments. (Use only with Group Code OA)): The impact of prior payer adjudication, including payments and adjustments.
  • N420 (Claim payment was the result of a payer's retroactive adjustment due to a Coordination of Benefits or Third Party Liability Recovery.): Says claim payment came from a retroactive adjustment due to coordination of benefits.
  • MA17 (We are the primary payer and have paid at the primary rate.): Says this payer is primary and paid at the primary rate, and you should arrange refunds with the other insurer.
  • N48 (Claim information does not agree with information received from other insurance carrier.): Used when claim information disagrees with information from the other insurance carrier.

N373 FAQ

Do I need to refund the other payer myself?

N373 says this payer is making the refund on your behalf. Watch for the other payer's recoupment or adjustment so you don't refund twice.

Why would one payer refund another?

When coordination of benefits is corrected, the true primary payer may settle the overpayment directly with the payer that paid first in error.

How should I post this?

Post the amount as the payer shows it, then reconcile it with the erroneous payer's remittance. Your net payment for the service should end up reflecting the correct order of benefits.