CO 237 denial code

Claim adjustment reason code 237. Often reported as CO 237.

Legislated or regulatory penalty

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 237 means

The payment was reduced by a penalty set by law or regulation, rather than by the payer's own policy.

A government rule imposes a reduction on this claim. Examples include penalties for not meeting electronic reporting, quality or other program requirements.

At least one remark code comes with it and points to the specific penalty. These reductions are usually not appealable through normal claim channels.

Group codes seen with 237

On a remittance, 237 comes after a group code. These are the ones it is most often reported with:

• CO 237 (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

• The provider did not meet a reporting or quality program requirement for the year.
• A program applied a legislated payment cut to the claim.
• The provider was flagged for not meeting electronic prescribing or similar requirements.

What to do next

1. Read the remark codes to identify the program behind the penalty.
2. Check the provider's status in that program for the year in question.
3. Use the program's own review process if you think the penalty was applied in error.
4. Post the reduction to an adjustment category separate from contractual write-offs.

Related codes

• 223 (reason code) Mandated adjustment with no specific code
• 45 (reason code) Charge exceeds the allowed amount