CO-237 is not about the service you billed. It is a penalty the payer applies because a law, a regulation or a plan rule says so. The best known example is the Medicare MIPS payment adjustment, which shows on every affected line. The code always comes with a remark that names the reason, so the remark is where the real work starts. (Primary source: X12 Claim Adjustment Reason Codes)
In brief: CARC 237 reads “Legislated/Regulatory Penalty.” It must carry a remark code. N807 points to a MIPS adjustment and N719 to plan requirements not met. Confirm the penalty applies to your clinician and year, check the amount, post it as a contractual adjustment, and use the program’s review process if it is wrong.
Part of our denial codes library. Written by Manikandan J, CPC, CRCR, who has posted Medicare payment adjustments for multi-specialty groups. Published 23 October 2026. Last updated: 23 October 2026. Code wording quoted word for word from X12.
What does CO-237 mean?
| Field | Value |
|---|---|
| Code | 237 |
| Description | “Legislated/Regulatory Penalty. At least one Remark Code must be provided (may be comprised of either the NCPDP Reject Reason Code, or Remittance Advice Remark Code that is not an ALERT.)” |
| Start | 06/05/2011 |
Source: X12 Claim Adjustment Reason Codes, checked 23 October 2026.
CO-237 is a penalty set by law or regulation, not a coding error. MIPS is the Merit-based Incentive Payment System, the Medicare program that raises or cuts Part B pay based on a past performance year; see the QPP MIPS overview. A payment adjustment is the percentage change applied to each paid line.
Common paired remarks:
- N807: “Payment adjustment based on the Merit-based Incentive Payment System (MIPS).”
- N719: “Penalty applied based on plan requirements not being met.”
Common causes of CO-237
- A negative MIPS adjustment. For example, a low score in a past performance year cuts pay in a later payment year.
- A plan rule penalty. Such as a reduced rate for a missed notice or reporting rule under the contract.
- Other legislated programs. For instance, hospital quality programs listed on the CMS value-based programs page.
Example scenario (fictional names), part 1
CO-237 Denial Example: What Happened
Laura Bennett runs revenue cycle for Ridgeview Family Medicine, a group with six clinicians. In January the Medicare remits began showing a small CAS*CO*237 line on every paid line for one physician, with remark N807.
Nothing changed in the coding. The other five clinicians were paid normally. The physician asked whether billing had made a mistake.
Is this a billing error or a penalty? Keep reading, or jump to how the CO-237 denial was resolved.
How to work CO-237
- Read the remark. It tells you which program or rule applies.
- Check eligibility and year. For MIPS, look up the clinician’s final score and payment adjustment in the QPP account.
- Check the math. Confirm the cut matches the published adjustment.
- Post it right. Post CO-237 as a contractual adjustment. It is not a patient balance.
- Ask for review if wrong. MIPS has a targeted review window; plan penalties follow the contract dispute process.
There is no claim form fix. Rebilling will not remove a penalty, so there is no before and after claim to show.
Example scenario (fictional names), part 2
How the CO-237 Denial Was Resolved
Laura checked the QPP feedback report. The physician had joined the group mid year and his prior practice had not reported quality data under his number.
Fix: She confirmed the negative adjustment matched his final score, posted the CO-237 lines as contractual write-offs and set up quality reporting for him in the current year.
Outcome: The physician understood the cut was a program penalty. The group now checks each new hire’s MIPS status during onboarding.
Names and details are illustrative; no real patient data.
CO-237 compared with nearby codes
| Code | Meaning | Fixable by rebill? |
|---|---|---|
| CO-237 | Legislated or regulatory penalty | No |
| CO-253 | Sequestration reduction | No |
| CO-45 | Above the allowed amount | No |
| CO-16 | Missing information | Yes |
See also our guide on how to read an explanation of benefits.
FAQ
What does CO-237 mean?
It is a penalty applied because of a law, regulation or plan rule. A remark code names the reason.
Is CO-237 a denial?
Usually not. The line is paid, but at a reduced amount.
What does N807 mean with CO-237?
The cut is a MIPS payment adjustment.
Can I bill the patient for CO-237?
No. Group code CO means the provider absorbs it.
Can I appeal a MIPS penalty?
You can request a targeted review in the program’s window if you think the score or adjustment is wrong.
Sources
How we checked: each code quote on this page was matched word for word with the X12 CARC and RARC lists on 23 October 2026.
- X12, Claim Adjustment Reason Codes (CARC 237). Accessed 23 Oct 2026.
- X12, Remittance Advice Remark Codes (N719, N807). Accessed 23 Oct 2026.
- CMS Quality Payment Program, MIPS overview. Accessed 23 Oct 2026.
- CMS, Value-Based Programs. Accessed 23 Oct 2026.
Last updated: 23 October 2026 ยท Educational content; not legal advice.