CO-252 — Additional documentation required
What it means
The payer paused the claim pending paperwork — notes, an itemized statement, or an attachment. Supplying exactly what they ask for usually gets it moving.
Standard definition (paraphrased): The payer has paused processing until it receives supporting paperwork or an attachment for this claim.
Why it happens
- • The payer wants clinical notes or an itemized bill before paying
- • An attachment referenced on the claim wasn't received
- • The service triggers a documentation review
Common next steps therapists take
- • Identify precisely which document the payer is requesting
- • Send exactly that (mind PHI-handling rules), then follow up on the claim's status
A blank appeal-letter template is available for this kind of denial — Out-of-network claim reconsideration.
Educational information only
This page is general educational information, not legal, billing, or medical advice, and not a determination about any specific claim. Denial codes are maintained by the X12 committee and updated periodically. Always verify code meanings, benefits, and requirements directly with the payer and against your own records.
Fewer denials start with a cleaner claim
Superbilled generates insurance-ready superbills with the correct codes and modifiers, so fewer claims come back with a code like CO-252 to decode.
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