OA-18 denial code
The payer already has this exact claim or service line.
“Exact duplicate claim/service (Use only with Group Code OA except where state workers' compensation regulations requires CO)”
Start 01/01/1995 · Last modified 06/02/2013 · X12 adjustment reason code list
What it usually means in behavioral health
Duplicates usually come from resubmitting a claim that's still processing, or sending a changed claim as a new one instead of a replacement.
Per diem programs add their own version: overlapping date spans on separate claims for the same stay.
Common causes
- Resubmitting a claim still in process
- Sending a changed claim as new instead of as a replacement
- Overlapping date spans across claims for one stay
- Same service entered twice in charge entry
Correct and resubmit, or appeal?
Don't appeal a true duplicate. Find the original claim's status. To change a processed claim, send a replacement claim (frequency code 7), or void it (frequency code 8), under the payer's rules.
What to do
Find the original claim and its status.
If a change is needed, send a replacement claim rather than a new one.
Fix overlapping date spans for per diem stays.
Stop automatic resubmission of claims that are still processing.
Got a OA-18 on your desk?
Send us the facts on that one denial — codes, payer, level of care, and dollar amount, no patient information — and within 2 business days we’ll tell you whether to correct or appeal, the deadline to watch, and what evidence would answer it. Free.