OA-23 Denial Code: Prior Payer Adjudication

The official definition

“The impact of prior payer(s) adjudication including payments and/or adjustments”

That is the verbatim definition of CARC 23 from the X12 Claim Adjustment Reason Code set, the standardized codes every insurer uses on EOBs and remittance advices. The letters in front of the number are the group code. OA: Other Adjustment: usually a coordination-of-benefits or other-payer adjustment.

What it means in plain English

You have two insurance plans, and this code shows how the first plan's payment affected what the second plan pays. OA-23 is coordination of benefits working as designed, not an error. The number it carries should match what your primary plan actually paid or adjusted, and that match is the thing to verify.

What to check on your EOB

• The primary plan's EOB for this same claim. The OA-23 amount on the secondary EOB should reflect what the primary actually paid or adjusted.
• Your total out-of-pocket across both plans. With dual coverage your share should generally be no more than what you'd owe under either plan alone.

What to do next

1. If the amounts don't match, send the secondary plan the primary plan's EOB and ask them to reprocess.
2. If the primary denied the claim, confirm the secondary processed it under its own benefits rather than just echoing the denial.
3. Keep both plans' EOBs together per claim; nearly every dual-coverage problem is solved by comparing the two documents.

Who's responsible

Usually no one; verify the amounts match. Most denials carry a clear owner. Knowing whether the fix belongs to you, your doctor, or the billing office is half the battle. If it's the provider's error, you should not be paying for it.

Want the fundamentals first? Start with how to read an EOB and the 7 most common billing errors. This page is general information about standardized denial codes, not legal or medical advice.