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OA-23 Denial Code: Impact of Prior Payer Adjudication

OA-23 means the adjustment reflects the impact of a prior payer's adjudication, including its payments and adjustments. It appears on secondary and tertiary remittances to explain why this payer's payment is reduced. It is informational, not a denial.

Quick facts

Code
OA-23 (CARC 23)
Status
Active In use since January 1, 1995; last modified September 30, 2012.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • OA (Other Adjustment): The only group X12 allows for CARC 23. The amount is accounted for by the prior payer's payment and adjustments, not assigned to the provider or patient by this payer.
Official description
The impact of prior payer(s) adjudication including payments and/or adjustments. (Use only with Group Code OA)
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What OA-23 means

CARC 23 describes the impact of prior payer adjudication, including payments and adjustments. X12 allows it only with group code OA. You’ll see it on secondary and tertiary ERAs: the payer is showing that part of the charge was already handled by the primary payer, so it isn’t paying that part again.

A simple secondary example:

  • Billed charge: $200
  • Primary allowed $140, paid $112, applied $28 to coinsurance
  • On the secondary ERA, OA-23 accounts for the portion the primary already paid or adjusted
  • The secondary then pays toward the $28 remaining patient responsibility, according to its own benefits and COB method

The exact OA-23 amount depends on how the secondary calculates coordination (for example, standard COB, non-duplication, or Medicare secondary payer rules).

Common causes of OA-23 questions

OA-23 itself is expected. Problems arise when the numbers behind it are off:

  • Primary payment reported incorrectly on the secondary claim, in the other-payer loops or in boxes 9 to 9d and 11d.
  • Primary adjustments omitted, so the secondary can’t see patient responsibility.
  • Wrong payer order, where the secondary is really primary.
  • Retroactive COB changes that reverse and reprocess payments (N420).
  • Secondary plan uses a non-duplication method, paying little or nothing when the primary paid what the secondary would have.

How to handle it

  1. Post the primary payment first, then the secondary ERA.
  2. Compare OA-23 to the primary’s payment and adjustments. They should reconcile.
  3. Check the remaining balance. It should equal any patient responsibility the secondary didn’t cover.
  4. If the secondary claim carried wrong primary data, correct it and send a corrected claim with resubmission code 7 in box 22.
  5. If the math still looks wrong, ask the secondary which COB method it used and request reprocessing.
  6. Bill the patient only for what remains as patient responsibility after all payers.

How to prevent problems

  • Send complete primary adjudication data electronically, including all CAS adjustments, not just the paid amount.
  • Verify coverage order at every visit.
  • Understand each secondary’s COB method so expected payments are realistic.
  • Reconcile secondary payments systematically. An ERA Analyzer can separate OA-23 from real denials and highlight secondary underpayments. See eligibility and COB denials.

Remark codes that may appear with OA-23

  • N4 (Missing/Incomplete/Invalid prior Insurance Carrier(s)): The prior carrier's EOB is missing, incomplete, or invalid, which can distort this calculation.
  • MA04 (Secondary payment cannot be considered without the identity of or payment information from the primary payer.): Secondary payment can't be considered without the primary's information.
  • N420 (Claim payment was the result of a payer's retroactive adjustment due to a Coordination of Benefits or Third Party Liability Recovery.): Payment resulted from a retroactive coordination of benefits or third-party recovery adjustment.
  • OA-22 (This care may be covered by another payer per coordination of benefits.): Another payer may be primary. OA-22 is sent before COB is resolved; OA-23 is sent once it is.
  • OA-136 (Failure to follow prior payer's coverage rules. (Use only with Group Code OA)): Failure to follow the prior payer's coverage rules.
  • PR-275 (Prior payer's (or payers') patient responsibility (deductible, coinsurance, co-payment) not covered. (Use only with Group Code PR)): The prior payer's patient responsibility isn't covered by this payer.
  • CO-276 (Services denied by the prior payer(s) are not covered by this payer.): Services the prior payer denied aren't covered by this payer.
  • CO-45 (Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement.): Fee schedule reductions, which may also appear on secondary claims.

OA-23 FAQ

Is OA-23 a denial?

No. It explains how much of the charge the primary payer already handled. The secondary's payment is calculated on what remains.

Should I write off an OA-23 amount?

Not as a separate adjustment. The OA-23 amount corresponds to the primary payer's payment and adjustments you already posted. Post the secondary payment and any remaining patient responsibility, and avoid double-counting.

What if the secondary paid less than expected after OA-23?

Check the primary payment and patient responsibility you reported on the secondary claim. If they were wrong or missing, correct and resubmit. If they were right, compare the secondary's calculation to its COB method and your contract.