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N423 Remark Code: Retro Adjustment, Non-Standard Program

N423 means the payment shown resulted from a payer's retroactive adjustment under a non-standard program. The payer reprocessed a previously adjudicated claim because of a special program or arrangement outside its usual payment rules.

Quick facts

Code
N423 (RARC N423)
Status
Active In use since August 1, 2007.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The adjustment follows program or contract terms between the payer and provider and does not by itself shift any amount to the patient.
  • OA (Other Adjustment): The payer may report the reversal of the original payment as an other adjustment alongside the reprocessed amount.
Official description
Claim payment was the result of a payer's retroactive adjustment due to a non standard program.
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What N423 means

N423 is the catch-all among the retroactive adjustment remarks. N419 covers rate changes, N420 covers COB and third party liability, N421 covers review decisions, and N422 covers contract incentive programs. When a payer reprocesses a claim for some other special program or arrangement, it uses N423 and labels it a non-standard program.

Because the code is broad, the remittance alone rarely tells you what happened. You will need the payer’s explanation to know which program triggered the change.

Examples of what may trigger it

  • A demonstration or pilot program with its own payment method.
  • A settlement or special agreement that required reprocessing past claims.
  • A one-time payer initiative, such as a targeted payment correction outside normal rate updates.

These are illustrations, not a complete list; the actual program depends on the payer.

What to do

  1. Ask the payer which program applied and whether a letter or statement explains the calculation.
  2. Match the reversal to the original payment and post only the net change to the account.
  3. Confirm patient cost sharing is unchanged, or adjust and refund if the payer’s reprocessing changed the patient’s share.
  4. Check the amount against the program terms or the notice you received.
  5. Dispute through the right channel. If the program was misapplied, use the dispute process the payer names for that program.

How to prevent surprises

Keep a record of any special programs, pilots, or settlements your organization has joined, with the payers and dates involved. When N423 appears, that record helps you connect the adjustment to its cause quickly instead of treating it as an unexplained takeback.

Codes that may appear with N423

  • CO-132 (Prearranged demonstration project adjustment.): A prearranged demonstration project adjustment, one type of non-standard program.
  • CO-45 (Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.): Shows the difference between charges and the new allowed amount after reprocessing.
  • N422 (Claim payment was the result of a payer's retroactive adjustment due to a payer's contract incentive program.): Retroactive adjustment under a contract incentive program specifically.
  • N419 (Claim payment was the result of a payer's retroactive adjustment due to a retroactive rate change.): Retroactive adjustment for a rate change.
  • N420 (Claim payment was the result of a payer's retroactive adjustment due to a Coordination of Benefits or Third Party Liability Recovery.): Retroactive adjustment for coordination of benefits or third party liability recovery.

N423 FAQ

What counts as a non-standard program?

The code does not define it. It can include demonstrations, pilots, special settlements, or one-time payer initiatives. Ask the payer which program it applied.

Is this a denial?

No. N423 explains a change to a claim that was already processed. The net effect can be positive or negative.

Can I appeal the adjustment?

You can dispute it if you believe the program was applied incorrectly. Because it comes from a program rather than a coverage decision, the payer may direct you to its provider dispute process.