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CO-186 Denial Code: Level of Care Change Adjustment

CO-186 means the payer adjusted payment because it changed the level of care billed, for example from inpatient to observation or from a higher to a lower level of facility care. It usually follows utilization review or a clinical determination.

Quick facts

Code
CO-186 (CARC 186)
Status
Active In use since June 30, 2005; last modified September 30, 2007.
Code set
Claim Adjustment Reason Codes (CARC)
Group codes
  • CO (Contractual Obligation): The difference between the billed and approved level of care is the provider's adjustment and isn't billable to the patient.
  • PR (Patient Responsibility): Sometimes the lower level of care shifts cost-sharing to the patient, for example different copays or coinsurance for outpatient versus inpatient care.
Official description
Level of care change adjustment.
X12 Claim Adjustment Reason Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What CO-186 means

CARC 186 reads “Level of care change adjustment.” The payer paid, but at a different level of care than the provider billed. The difference between the billed level and the approved level is reported with this code.

Level of care matters most in facility settings: inpatient versus observation, acute versus sub-acute, residential versus partial hospitalization or intensive outpatient, and different skilled nursing or home health levels. Utilization review, medical necessity criteria, or authorization terms usually drive the change.

Example: a hospital bills an inpatient stay. On review, the payer decides the patient met observation criteria only and pays under its observation methodology. The difference appears as CO-186 with N610 or N188.

Common causes

  • Admission criteria not met under the payer’s clinical guidelines.
  • Authorization approved a lower level than the level billed.
  • Concurrent review downgrade partway through the stay.
  • Documentation gaps in physician notes that fail to show intensity of services.
  • Revenue codes or bill type not matching the approved level.
  • Missed notification deadlines for an admission, leaving the payer to decide the level after the fact.

How to fix it

  1. Compare the approved level in the authorization or review letter with what was billed.
  2. If the claim billed the wrong level, submit a corrected institutional claim with the appropriate bill type frequency code.
  3. If you disagree, request peer-to-peer review if still available, then file a clinical appeal with the record and criteria.
  4. Coordinate with professional billing so physician claims match the final level.
  5. Post the accepted difference as a contractual adjustment.

How to prevent it

  • Apply level-of-care criteria at admission with case management review.
  • Obtain and track authorizations for the specific level of care, and update them when the level changes. See authorization denials.
  • Train physicians to document severity, risk, and planned intensity of services.
  • Monitor downgrades by payer to find patterns worth contract discussion. ERA Analyzer can surface them from your ERAs.

Specialty notes

Behavioral health facilities often see level of care changes between residential, partial hospitalization, and intensive outpatient programs, each of which may need its own authorization.

Remark codes that may appear with CO-186

  • N188 (The approved level of care does not match the procedure code submitted.): The approved level of care doesn't match the procedure or revenue code billed.
  • N610 (Alert: Payment based on an appropriate level of care.): Payment was based on the level of care the payer considered appropriate.
  • M26 (The information furnished does not substantiate the need for this level of service.): The information furnished doesn't substantiate the need for the level of service billed.
  • CO-150 (Payer deems the information submitted does not support this level of service.): Documentation doesn't support the level of service, used more for professional services.
  • CO-152 (Payer deems the information submitted does not support this length of service.): Documentation doesn't support the length of service, such as days of care.
  • CO-169 (Alternate benefit has been provided.): An alternate, usually less costly, benefit was paid.

CO-186 FAQ

When does CO-186 usually appear?

Most often on institutional claims: inpatient admissions converted to observation, residential treatment paid at a lower level, or skilled nursing and home health levels changed after review.

Can I appeal a level of care change?

Yes. Clinical appeals typically need the physician's documentation of severity and intensity of services, and any payer criteria the case met. Many payers also offer peer-to-peer review.

Does CO-186 affect the professional claim?

It can. If the facility level changes, physician services may need different codes or places of service. Coordinate between facility and professional billing.

Is CO-186 a denial?

It's a payment adjustment rather than a full denial. The payer paid for care at the level it approved and adjusted the rest. It can still represent a large amount on an inpatient claim.