OA-18

Denied as a duplicate claim

The plan already processed this same claim. It usually isn't something you owe twice. Check that the first claim was paid.

Official meaning (X12 code 18): Exact duplicate claim/service.

Who pays

OA-18. Other adjustment: used when neither CO nor PR applies, often for coordination with another payer.

What to do

Find the original claim on your EOBs.
If the original was paid, ignore any second bill for it and tell the provider.
If you really had the service twice, the provider should resubmit with the right modifier.

If you appeal

Denials for a wrong code, missing modifier or mismatched diagnosis are usually fixed when the provider's billing office corrects and resubmits the claim. Call them first and ask them to do it; still file the appeal before the deadline as a backstop.

What the appeal asks for: Reprocess this claim once the provider submits corrected coding; the service itself was covered and medically necessary.

Deadlines for the first appeal

employer plan: 180 days from the notice
ACA Marketplace plan: 180 days from the notice
Medicare Advantage plan: 65 days from the notice
Original Medicare: 120 days from the notice
Medicaid: 60 days from the notice

The date printed on your notice controls. Urgent care can be appealed on an expedited (72-hour) basis.

What the data show

11.5%Only 11.5% of denied Medicare Advantage prior authorization requests were appealed in 2024. KFF, 2024 data

80.7%80.7% of appealed Medicare Advantage prior authorization denials were partially or fully overturned in 2024. KFF, 2024 data

<1% (262,982 appeals)Fewer than 1% of denied in-network marketplace claims were appealed in 2024 (at least 262,982 appeals). KFF, 2024 data

66% upheldInsurers upheld 66% of denials on internal appeal in 2024 (165,863 denials). KFF, 2024 data

25%25% of in-network marketplace denials were for administrative reasons, the most common reason other than 'other'. KFF, 2024 data

Averages across all denials; not a prediction for yours.

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General information, not legal or medical advice. Owed is a document-preparation and sending service, not a law firm.