OA 23 denial code

What OA-23 means

OA-23 appears on remittances from a secondary or tertiary payer. It reports the impact of the prior payer’s adjudication (the money the primary payer already paid plus the adjustments it already took), so the secondary remittance balances against your billed charge. The group code OA means “other adjustment”: neither a provider write-off in the usual contractual sense nor patient responsibility. It is accounting glue, not a denial.

A worked example. You bill $200 to the primary. The primary allows $120 (a $80 contractual adjustment), pays $96, and leaves $24 coinsurance. You bill the secondary. Its remittance might show OA-23 for $176 (the primary’s $96 payment plus the $80 adjustment) and then pay some or all of the $24 that remained. The OA-23 amount is not new money lost; it is the prior payer’s activity restated so the secondary claim adds up.

Medicare uses this code when it processes as the secondary payer under MSP rules, and commercial payers use it the same way in coordination-of-benefits situations.

Common causes

You should expect OA-23 on essentially every correctly processed secondary claim. Situations that put it in front of you:

1. Medicare Secondary Payer claims: a working-aged patient with employer group coverage primary, Medicare secondary.
2. Commercial-plus-commercial coordination of benefits, such as a patient covered under their own plan and a spouse’s plan.
3. Medicare crossover claims to a Medigap or Medicaid payer, where the secondary remittance restates Medicare’s payment and adjustments.

The problem cases are almost always data problems: the primary payer’s payment and adjustment amounts (the CAS segment data from the primary 835) were keyed or transmitted wrong on the secondary claim, so the secondary payer’s OA-23 does not reconcile, or the claim rejects for unbalanced amounts.

How to fix and resubmit

Most of the time there is nothing to fix, only to post correctly:

1. Post OA-23 as an informational offset, not a write-off and not patient responsibility. Your primary remittance already posted the payment and contractual adjustment it represents; do not post them twice.
2. Reconcile: primary payment + primary adjustments should equal the OA-23 amount. If it does, the claim processed normally.
3. If it does not reconcile, compare the secondary claim’s reported prior-payer amounts against the actual primary 835. Correct the amounts and resubmit the secondary claim.
4. If the secondary paid $0 with only OA-23 and the primary genuinely left a balance, check whether the secondary claim carried the primary’s patient-responsibility amounts correctly. Secondaries pay against what the primary left, and bad COB data makes that look like zero.
5. Never appeal OA-23 itself. If the secondary payment is wrong, the dispute is about the underlying benefit calculation, and the payer’s policy governs.

How to prevent it

• Automate secondary claim creation from the primary 835 so payment and adjustment data transfer without manual keying.
• Verify coordination of benefits at check-in: a 270/271 eligibility check plus asking the patient about other coverage keeps primary and secondary in the right order and avoids CO-22 denials.
• Train payment posters to recognize OA-23 on sight so it never gets posted as a contractual loss or pushed to a patient statement.