OA-23 is not a denial. On a secondary remittance it shows the amount already handled by the primary payer, its payment and its adjustments. Post it as an adjustment and look at what the secondary actually paid or assigned to the patient.
The official wording
The X12 Claim Adjustment Reason Code list defines 23 as: "The impact of prior payer(s) adjudication including payments and/or adjustments. (Use only with Group Code OA)"
The letters in front are the group code. CO means contractual obligation (the provider absorbs it), PR means patient responsibility, and OA is other adjustment. The same reason code can come with different group codes, so always read both.
What OA-23 is telling you
When a payer processes a claim as secondary, it accounts for what the primary already paid. OA-23 is the line that carries that amount. X12 allows it only with group code OA. It does not mean anything went wrong.
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When it is worth a second look
- The OA-23 amount does not match the primary EOB. The secondary may have read the primary amounts wrong.
- The secondary paid zero even though the primary left a patient balance the secondary should cover.
- The primary EOB was not sent with the claim, which can lead to wrong amounts.
How to post it
- Post OA-23 as an informational adjustment, not as a write-off or denial.
- Compare it with the primary EOB. If it does not match, call the secondary with both documents.
- Bill the patient only what the secondary assigned as PR (deductible, coinsurance, copay).
One secondary claim, line by line
The primary plan allowed $150, paid $120 and left $30 coinsurance. The claim then went to the secondary plan.
| Line on the secondary remittance | Amount | What it means |
|---|---|---|
| Billed charge | $200.00 | Your charge |
| OA-23 | $170.00 | What the primary already handled: $120 paid plus $50 adjusted |
| Paid by secondary | $30.00 | The secondary paid the coinsurance |
| Patient balance | $0.00 | Nothing left |
Check: $170 OA-23 + $30 paid = $200 billed. If the numbers do not add up, the secondary may have read the primary EOB wrong.
How to post OA-23
- Post the primary payment and adjustments first, from the primary EOB.
- On the secondary remittance, treat OA-23 as information. Do not post it again as a second write-off.
- Post the secondary payment.
- Move any PR amounts from the secondary to the patient.
- If the totals do not match, call the secondary with both EOBs.
OA-23 checklist
- ☐ The primary EOB was sent with the secondary claim.
- ☐ The OA-23 amount matches the primary's payment and adjustments.
- ☐ You did not write off the same amount twice.
- ☐ The patient is billed only what the secondary marked as PR.
Questions people ask about OA-23
Is OA-23 a denial?
No. It reports the primary payer's payment and adjustments on a secondary claim.
Should OA-23 be written off?
It is an adjustment that reflects what the primary handled. Post it so the balance matches, and check what the secondary paid and what it assigned to the patient.
Why does OA-23 only use group code OA?
X12 allows reason 23 only with group code OA, because it reports what another payer did, not a new decision by this payer.
Should I write off the OA-23 amount?
No, not a second time. The primary payment and adjustments were already posted. OA-23 just shows them on the secondary remittance.
What if the secondary paid nothing?
Check whether the primary already paid the full allowed amount, or whether the secondary used the wrong primary amounts. Call with both EOBs if it looks wrong.
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PR-1 · PR-2 · PR-3 · CO-4 · CO-5 · CO-11 · CO-15 · CO-16 · OA-18 · CO-22 · OA-23 · CO-24 · CO-26 · CO-27 · CO-29 · CO-31 · CO-45 · CO-49 · CO-50 · CO-59 · PR-96 · CO-97 · CO-109 · CO-119 · CO-129 · CO-140 · CO-146 · CO-151 · CO-167 · CO-170 · CO-181 · CO-185 · CO-197 · CO-198 · PR-204 · CO-234 · CO-236 · CO-242 · CO-252 · CO-253 · CO-288 · CO-A1 · CO-B7 · MA130 · N130 · N23 · N290
Timely filing limits by payer: Cigna timely filing limit · HealthSpring timely filing limit · Aetna timely filing limit · UnitedHealthcare timely filing limit · Humana timely filing limit · corrected claim timely filing limits
Sources: X12 Claim Adjustment Reason Code list (23), read October 27, 2026; CMS Medicare guidance where Medicare rules are mentioned; Example amounts are for illustration only. Last reviewed October 27, 2026. General information, not coding or legal advice. Payer rules differ, so check the remark code and the payer's own policy.