CO-194 means the payer won’t pay the anesthesia line. The claim says the surgeon, the assistant or the attending doctor gave it. Most plans fold that into the surgery fee. They pay a separate anesthesia code only when someone else does the work, such as a nurse anesthetist. (Primary source: X12 Claim Adjustment Reason Codes)
In brief: CARC 194 reads “Anesthesia performed by the operating physician, the assistant surgeon or the attending physician.” Check the anesthesia record. If someone else gave it, bill under that person’s NPI with the right modifier. If the surgeon gave it, the code isn’t paid on its own. Sedation codes may fit instead.
Part of our denial codes library. Written by Manikandan J, CPC, CRCR, who has audited anesthesia and endoscopy billing for multi-specialty groups. Published 22 October 2026. Last updated: 22 October 2026. Code wording quoted word for word from X12.
Official CARC 194 description
| Field | X12 text |
|---|---|
| Code | 194 |
| Description | “Anesthesia performed by the operating physician, the assistant surgeon or the attending physician.” |
| Start | 02/28/2006 |
| Last modified | 09/30/2007 |
Source: X12 Claim Adjustment Reason Codes, checked 22 October 2026.
Anesthesia billing basics
Anesthesia codes are the 00100-01999 range. They’re billed with base units plus time. Anesthesia modifiers are two-letter codes that say who gave it. For example:
- AA: the doctor gave it in person.
- QK: a doctor directed two to four cases at once.
- QX: a CRNA gave it with a doctor directing.
- QZ: a CRNA gave it alone.
Moderate sedation is a lighter level, billed with 99151-99157. The doctor doing the procedure may bill it when the plan allows.
Example scenario (fictional names), part 1
CO-194 Denial Example: What Happened
Tanya Brooks bills for Riverbend Digestive Health. Dr. Kevin Osei did a diagnostic colonoscopy (45378) for melena (K92.1). A nurse anesthetist (CRNA) on staff, Aaron Feld, gave the anesthesia. It was billed with 00811.
The system put the 00811 line under Dr. Osei’s NPI in Box 24J. It had no modifier. The claim went to Ashgrove Health Plan, a fictional commercial plan. The 835 paid 45378 but showed CAS*CO*194 on 00811 with remark LQ*HE*N95, “This provider type/provider specialty may not bill this service.”
Had the surgeon really given anesthesia, or did the claim just say so? Keep reading, or jump to how the CO-194 denial was resolved.
Why payers apply reason code 194
- Wrong NPI. The system copies the surgeon’s NPI from the procedure line.
- No modifier. Without AA, QK, QX, QY or QZ, the payer can’t tell who gave it.
- The surgeon gave it. For example, a surgeon gives a nerve block during their own case. That’s part of the surgery fee.
- The assistant billed it. An assistant or attending doctor billed a code for the same case.
How to fix a CO-194 denial
- Pull the record. It shows who gave it, the start and stop times, and who directed.
- Compare it with the claim. Check Box 24J and the modifier.
- If a CRNA or other doctor gave it, fix the NPI in Box 24J. Add the right modifier, such as QZ.
- Check the time. Put it in Box 24G the way the plan wants, as minutes or units.
- Send a corrected claim with code 7 and the first claim number in Box 22.
- If the surgeon gave it, don’t rebill the code. See if sedation codes fit, or write the line off.
Example scenario (fictional names), part 2
How the CO-194 Denial Was Resolved
Tanya opened the anesthesia record. Aaron Feld gave care for the whole case and signed the record. No doctor directed him. The charge link had copied Dr. Osei’s NPI from the scope line.
Fix: a corrected claim with Box 22 code 7 and the original claim number. The 00811 line now had modifier QZ, his NPI in Box 24J and the minutes in Box 24G.
Outcome: Ashgrove paid the anesthesia line. Riverbend fixed the link so these lines take the NPI from the record.
Names and details are illustrative; no real patient data.
UB-04 not shown: who gave the anesthesia, and its modifier, go on the CMS-1500 only. No UB-04 field holds them.
- Box 24D modifier: QZ added (CRNA service without medical direction by a physician).
- Box 24J: rendering NPI changed from Dr. Kevin Osei (surgeon) to Aaron Feld, CRNA (placeholder NPI).
- Box 24G: anesthesia minutes from the anesthesia record (placeholder 30).
- Box 22: resubmission code 7 with the original claim number.
- Box 21: K92.1, entered as K921, is unchanged.
CARC 194 vs related codes
| Code | What it says | Key difference |
|---|---|---|
| CO-194 | Anesthesia by the operating, assistant or attending physician | Who gave it |
| CO-97 | Included in another service already paid | General bundling |
| CO-185 | Rendering provider not eligible for the service | Provider eligibility |
| CO-4 | Procedure code inconsistent with the modifier | Modifier mismatch |
Prevention checklist
- Take the NPI for each anesthesia line from the record, not the procedure line.
- Require a modifier on every 00100-01999 line.
- Flag claims with the surgeon’s NPI on both lines.
- Teach staff when sedation codes apply instead.
Recap
CO-194 means the claim said the surgeon gave the anesthesia. If someone else did, fix Box 24J and the modifier and resend. If the surgeon did, the code isn’t paid on its own.
FAQ
What does CO-194 mean?
The payer says the surgeon, the assistant or the attending doctor gave it, so the code isn’t paid on its own.
Can a surgeon bill anesthesia codes?
Not for their own case, as a rule. Some plans pay sedation codes instead.
Which modifier shows a CRNA without medical direction?
QZ. Use QX when a doctor directs the CRNA.
Where does the anesthesia provider’s NPI go?
Box 24J on the CMS-1500, on the anesthesia line.
Can I bill the patient for a CO-194 line?
No. Group code CO keeps the amount with the provider.
Sources
How we checked: each code quote on this page was matched word for word with the X12 CARC and RARC lists on 22 October 2026.
- X12, Claim Adjustment Reason Codes (CARC 194, 97, 185, 4). Accessed 22 Oct 2026.
- X12, Remittance Advice Remark Codes (N95). Accessed 22 Oct 2026.
- CMS, Medicare Claims Processing Manual, Chapter 12 (physicians and nonphysician practitioners). Accessed 22 Oct 2026.
- NUCC, 1500 Claim Form instructions. Accessed 22 Oct 2026.
Last updated: 22 October 2026 · Educational content; not legal advice.