Denial Code Deep Dive: CO-18
Seven patterns hiding
behind one word: duplicate.
CO-18 is the code teams question the least. This is what’s actually underneath it.
Across an analysis of more than 70,000 denied claims, five codes accounted for nearly half of all denial volume. CO-18 sits second on that list at 12.3%, and it turns out to be the least literal of the group. It sorts into seven distinct patterns, and a genuine, no-action-needed duplicate is only one of them.
What you will learn:
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The seven patterns hiding inside CO-18
Share of volume and owning team for each one
Why “confirmed duplicate” is the payer’s opening assertion
The two fields auto-adjudication logic skips
What to do with the half that carry no remark code at all