Denial code CO-236: Procedure or modifier combination not compatible
This combination of procedure and modifier is not allowed with another service on the same day (NCCI edit).
At a glance
| Code | CO-236 (group CO, reason 236) |
| Who owes it | Contractual obligation: The provider must write this off. The patient cannot be billed for it. |
| Type | Bundling / modifier |
| Worth appealing? | Usually yes, once the cause is fixed |
How to fix it
- Review the NCCI pair and whether a modifier is allowed.
- Correct with modifier 59/X{EPSU} if documented, or accept the denial.
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Start free for 14 daysFrequently asked questions
What does denial code CO-236 mean?
This combination of procedure and modifier is not allowed with another service on the same day (NCCI edit).
How do I fix a CO-236 denial?
1. Review the NCCI pair and whether a modifier is allowed. 2. Correct with modifier 59/X{EPSU} if documented, or accept the denial.
Should I appeal a CO-236 denial?
Usually yes, or send a corrected claim. CO-236 denials are often recoverable once the cause is fixed. Check the payer's appeal deadline (often 60 to 180 days, 120 days for Medicare redeterminations).
Can I bill the patient for CO-236?
No. With group code CO the amount is not the patient's responsibility and must be written off unless it is overturned.
Plain-English summary for billing staff, not the official code text. See x12.org/codes for the official wording, and always follow the payer's own policy.