OA — Other adjustment — most often coordination of benefits.
So it belongs to neither side yet. Work the coordination of benefits before you treat any of it as lost money.
The same code, a different prefix. 109 also arrives as CO 109. The reason for the denial is the same. The prefix decides who pays for it, so the next step is not the same. If your remit says CO 109, read that page instead.
Fix and resubmit. This is a correction, not an appeal. Appealing burns the deadline.
In the order we see it.
The claim went to the wrong payer or the wrong contractor.
A Medicare Advantage patient was billed to traditional Medicare.
Identify the correct payer and rebill.
The documentation, not the argument.
Identification of the correct payer, and a rebill to them.
The common mistake. Do not appeal. Find the right payer and rebill, watching the new payer's filing window.
Where this comes from. This is our own reading of the code, not the payer's and not a copy of the standards text. We classify it from how these denials actually resolve. Where we are unsure, we say so rather than guessing.
Send your denial summary for the last ninety days. Four columns: payer, CARC code, count, billed amount. I will tell you which were winnable and what they were worth.
Send your denial summary No patient data. No BAA. No charge.