CO 250 denial code

Claim adjustment reason code 250. Often reported as CO 250.

Wrong attachment sent

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What 250 means

The payer got an attachment, but it was not the document it asked for, so the needed one is still missing.

You sent something, but it did not answer the payer's request. A wrong date of service, a wrong patient or the wrong type of record are common reasons.

At least one remark code comes with it and names the document the payer still needs. Send that document rather than rebilling the claim.

Group codes seen with 250

On a remittance, 250 comes after a group code. These are the ones it is most often reported with:

• CO 250 (Contractual Obligation): The provider's side of the ledger. The reduction comes from the payer contract or a rule the provider has to follow, and the patient normally cannot be billed for it.

The payer chooses the group code for each adjustment, so the same reason code can appear with another group code on your remittance. Read the two together. More about group codes.

Common causes

• Records for a different date of service were attached.
• A progress note was sent when the payer asked for an operative report or certification.
• The attachment control number linked the file to the wrong claim.
• A scanned document was blank, unreadable or for another patient.

What to do next

1. Read the remark codes to see which document the payer expects.
2. Pull the correct document and check the patient, date and document type before sending.
3. Resend it with the claim number and attachment control number that match.
4. Check your attachment workflow if wrong files go out repeatedly.

Related codes

• 226 (reason code) Provider did not send requested info
• 16 (reason code) Missing information or billing error
• 252 (reason code) Attachment or documentation required