Denial Code OA-23

What OA-23 means

This line reflects what the primary payer already paid or adjusted, so the secondary payer can calculate its share — it's an accounting adjustment, not a denial.

Why OA-23 happens

• A secondary payer is accounting for the primary payer's payment and adjustments before paying its portion
• Medicare as secondary payer is reducing for an employer group health plan's prior payment
• A standard coordination-of-benefits calculation between two payers
• The primary remittance reduced the allowed amount the secondary recognizes

What to do when you get OA-23

1. 1Confirm the OA-23 amount matches what the primary payer actually paid/adjusted on its EOB
2. 2Verify the secondary calculated its payment off the correct primary allowed amount
3. 3Reconcile the patient balance after the secondary pays (deductible/coinsurance may still apply)
4. 4If the math is wrong, resubmit the primary EOB and confirm COB is set up correctly

OA group code: who absorbs the charge

Appeal, correct, or write off OA-23?

OA-23 is grouped under OA (Other Adjustment) precisely because it is neither a contractual write-off you owe nor a balance the patient owes — it is informational coordination between payers, so it rarely needs an appeal. Act only when the secondary payer mis-read the primary's payment: then re-send the primary EOB and request a reprocessing, which is a correction rather than a formal appeal.

Example

A patient has a commercial plan primary and Medicare secondary. The commercial plan pays $80 of a $130 allowed service. When the claim crosses over to Medicare, the remittance shows an OA-23 adjustment reflecting the primary's $80 payment so Medicare can compute any remaining secondary liability. No provider action is needed if the amounts reconcile.

Prevent OA-23 going forward

• Always attach the primary EOB/ERA to secondary claims
• Keep COB order accurate so crossovers calculate correctly
• Reconcile secondary payments against the primary remittance line by line
• Confirm automatic crossover is active for Medicare/Medigap where applicable

Code families most affected

• All services for patients with secondary coverage
• Medicare-secondary and Medigap crossover claims
• Any multi-payer coordination-of-benefits scenario

Related codes

Payer notes

OA-23 is used only with Group Code OA by X12 design, which is the giveaway that it is purely a coordination adjustment. It is informational: the dollars move the math along between payers and should not be written off as contractual or billed to the patient on their own.