Denial code CO-252: Attachment or documentation required
An attachment (records, report, invoice) is needed to process this claim.
At a glance
| Code | CO-252 (group CO, reason 252) |
| Who owes it | Contractual obligation: The provider must write this off. The patient cannot be billed for it. |
| Type | Missing information |
| Worth appealing? | Usually yes, once the cause is fixed |
How to fix it
- Send the attachment with the payer's attachment control number (PWK).
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Start free for 14 daysFrequently asked questions
What does denial code CO-252 mean?
An attachment (records, report, invoice) is needed to process this claim.
How do I fix a CO-252 denial?
1. Send the attachment with the payer's attachment control number (PWK).
Should I appeal a CO-252 denial?
Usually yes, or send a corrected claim. CO-252 denials are often recoverable once the cause is fixed. Check the payer's appeal deadline (often 60 to 180 days, 120 days for Medicare redeterminations).
Can I bill the patient for CO-252?
No. With group code CO the amount is not the patient's responsibility and must be written off unless it is overturned.
Plain-English summary for billing staff, not the official code text. See x12.org/codes for the official wording, and always follow the payer's own policy.