CO-234 denial code
This procedure is not paid separately — and the remark code next to it says why. The payer isn't disputing that you did it; they are saying its payment lives inside something else on the claim, or that on its own it isn't a payable line at all.
CO — Contractual Obligation. The write-off is yours. You agreed to it in your contract with the payer, and you cannot bill the patient for it.
Why you got it
- 1The service is considered a component of another procedure billed the same day.
- 2An add-on style code was billed without the primary service it attaches to.
- 3Payer payment policy folds this service into a global or composite payment.
How do I fix a CO-234 denial?
- Read the remark code first — CO-234 never travels alone, and the RARC carries the actual reason.
- Check whether the primary procedure was billed and paid. An add-on denied because its primary is missing is fixed by sorting out the primary, not by appealing the add-on.
- If the service genuinely stands alone — separate session, separate site, separate indication — appeal with documentation that shows the separation. If it doesn't, the write-off is correct and it is contractual, not billable to the patient.
How to stop the next one
Know your add-on pairings and the services your major procedures absorb. That knowledge is published payment policy, and checking it at coding time is cheaper than discovering it at posting time.
Our diagnosis scrubber will not catch this one. CO-234 is driven by procedure codes, modifiers, or eligibility rather than by the diagnosis set — and procedure-side checking needs CPT codes, which aren’t included yet. We would rather tell you that than sell you a tool that quietly misses your most common denial.
If denials like this are a volume problem rather than a one-off, the denial management page explains how the paid workspace catches the coding causes on every claim, and the free ICD-10-CM lookup shows the coding notes behind any diagnosis code on the remittance.