252: An attachment/other documentation is required to adjudicate this claim/service.
The payer needs supporting documentation, such as medical records, operative notes, or an itemized statement, before it can process this claim or line item.
What the group code means
- CO
- Contractual Obligation. The provider is responsible and the amount cannot be billed to the patient.
Why it fires
- The payer's policy requires documentation for this code or procedure type, such as unlisted codes, high-dollar DME, or certain modifiers
- The claim was submitted without the required attachment or with an incomplete one
- The payer flagged the claim for pre-payment review requiring records
Corrective actions, ranked
- 1
Identify exactly what is needed
Check the remark code or payer correspondence for the specific document requested, such as an op note, letter of medical necessity, or invoice.
- 2
Submit the documentation promptly
Send the requested records through the payer's preferred method, such as portal, fax, or mail, referencing the claim number.
- 3
Track the resubmission
Follow up to confirm the documentation was received and matched to the claim before the timely filing or appeal window closes.
Is it worth appealing
This is really a documentation request rather than a final denial. Submitting complete records promptly typically resolves it without a formal appeal.
Retrieved 2026-07-18.
Do not let this happen again
Scrub the claim against NCCI PTP and MUE edits before you submit, free and in your browser.
DenialPath provides billing and administrative guidance based on published CMS and X12 sources. It is not medical advice, not a coverage determination, and not a guarantee of payment. NCCI and MUE edits are republished quarterly and payer policies vary by contract. Always confirm against the payer's own current policy before submitting or appealing.