Specialty
Anesthesia billing services
Anesthesia billing services price every case from three inputs: the base units of the anesthesia code, the minutes from when the anesthesia practitioner starts preparing the patient until the patient is safely handed to postoperative care, and the modifier that says who did the work and how many rooms were running at once.
See where claims are getting stuck. No patient data needed.
Get one wrong and the claim pays the wrong amount or nothing. Remitwright gives anesthesia groups, CRNA practices and hospital-based departments a dedicated biller who captures time to the minute, applies the direction and concurrency rules case by case, bills the physician and nurse anesthetist lines the way the manual says, and works denials to the cause.
Anesthesia billing is one of Remitwright's specialty billing services, each set out with its own code families, denial reasons and payer rules.
Last reviewed by the Remitwright billing team. Editorial policy
- 00100-01999
- 36555
- 62320-62327
Denials
Why anesthesia claims get denied
The reasons that come up most on anesthesia remittances, with the usual cause and the fix. Code explanations are our own; the official list is maintained by X12.
| Code | Reason | Usual cause | The fix |
|---|---|---|---|
| CO-4 | Payment modifier missing or mismatched | No payment modifier on the line, QS sent alone, QZ on an anesthesiologist assistant who by definition works under direction, or a QX line with no matching QK or QY line from the physician | Modifier logic built into charge capture per practitioner type and per case, with the physician and CRNA lines reconciled before release |
| CO-16 | Minutes missing or sent as units | Time units entered where the payer wants minutes, or start and stop times missing from the anesthesia record so minutes cannot be computed or defended | Minutes captured from the anesthesia record's documented start and stop times, with a claim edit that rejects whole units in the time field |
| CO-97 | Part of the anesthesia package | The pre-anesthesia evaluation or the routine recovery room check billed as a visit, or a nerve block billed for postoperative pain when the anesthetic itself was monitored anesthesia care or moderate sedation | The anesthesia package rules applied at coding, with blocks released only when the mode of anesthesia and the surgeon's request both support them |
| CO-236 | Two anesthesia codes for one session | Two anesthesia codes reported for one operative session instead of the highest-base code with modifier 51 and the combined minutes | One anesthesia line per session, chosen by base units, with all minutes on it |
| CO-18 | Already billed; treated as a duplicate | The physician and the CRNA both billed the full rate for one case without documentation from each that both were medically necessary, or the group sent the case twice from two schedules | One case record per patient per date that both lines are built from, with the dual-provider documentation attached when AA and QZ are both used |
| CO-151 | Units exceed what the payer allows | Minutes far out of line with the surgeon's operative time, daily epidural management billed more than once a day, or billed on the day the catheter was placed | Time compared to the operative record before release, and epidural management counted once per postoperative day starting the day after insertion |
| CO-B7 | Anesthetist not enrolled on that date | A CRNA or anesthesiologist assistant not yet enrolled or not reassigned to the group, or a claim without the billing number of the practitioner or employer who furnished the service | Every anesthetist tracked against every payer with effective dates, and claims held for a new hire until enrollment is confirmed |
| CO-197 | No authorization that matches the case | A commercial plan authorized the surgery under a different code or site than the one performed, so the anesthesia claim that rides on it is denied as well | The surgical authorization pulled from the facility schedule before the case and compared to the code and site actually billed, with mismatches sent back to the surgeon's office before the case |
Codes
Common anesthesia codes and modifiers
Code families by number with our own one-line explanations. CPT descriptors belong to the AMA and are not reproduced here.
| Codes | What the family covers |
|---|---|
| 00100-01999 | The anesthesia codes, arranged by body region and type of operation. Each carries a base unit value that Medicare publishes once a year and left unchanged for 2026; the claim reports actual minutes, and the contractor turns them into time units. |
| 01996 | Daily management of a continuous epidural or spinal catheter after surgery, payable on days after the operation but not on the day the catheter was placed, and limited to one unit per day however many visits it takes. |
| 36555, 93503, 31500 | Central venous lines, pulmonary artery catheters and emergency intubation outside the operating suite, the procedures the manual names as separately payable to anesthesiologists and non-directed CRNAs alongside the anesthesia. |
| 62320-62327, 64400-64530 | Epidural and peripheral nerve block injections, separately reportable for postoperative pain only when the surgeon asks for the help, documents why, and the mode of anesthesia for the operation allows it. |
| 99291-99292 | Critical care, which an anesthesiologist may report only for significant, separately identifiable ongoing care after the anesthesia service has ended, never for routine recovery room follow-up. |
Modifiers that matter
- AA
- The anesthesiologist personally performed the whole case, or was continuously involved in one case with a student nurse anesthetist. Paid at the full personally performed rate.
- QK
- The physician medically directed two, three or four concurrent cases staffed by qualified individuals and performed all seven required activities. Paid at half of the personally performed allowance, and concurrency counts every patient in every room, Medicare or not.
- QY and QX
- One CRNA or anesthesiologist assistant directed by one anesthesiologist. The physician reports QY and the nurse anesthetist reports QX, ordinarily with the same minutes on both lines.
- QZ
- A CRNA working without medical direction. Also the CRNA's modifier when the physician and the CRNA each furnish a medically necessary service in the same case, in which case the physician reports AA and both document why both were needed.
- AD
- The anesthesiologist was involved in more than four concurrent cases or was doing other work while directing. The contractor allows three base units, plus one time unit if the record shows the physician was present at induction.
- QS, G8 and G9
- Monitored anesthesia care, for information only. Each must travel with actual minutes and one of the payment modifiers; on its own it is not a payable line.
- 51
- Multiple surgeries under one anesthetic. The anesthesia code with the highest base units carries modifier 51 and the total minutes for every procedure in the session, and payment uses that code's base units with the combined time.
- 59 or XU
- On an epidural or peripheral nerve block billed on the same date as the anesthesia, to show it was placed for postoperative pain at the surgeon's request rather than as part of the anesthetic.
- 23 and 47
- Unusual anesthesia, and anesthesia by the surgeon. Medicare's manual says contractors may not adjust fee schedule amounts for either one, so on a Medicare claim neither raises the payment.
Payers
Payer notes
- MedicareThe fee schedule amount is the allowable base units plus time units, multiplied by an anesthesia conversion factor specific to the locality. One time unit is 15 minutes; the contractor divides the reported minutes by 15 and rounds to one decimal, and recognizes no time units for daily epidural management. Anesthesia time starts when the practitioner begins to prepare the patient in the operating room or an equivalent area and ends when the patient may be safely placed under postoperative care, and blocks around an interruption may be added as long as continuous care was being furnished within them.1
- MedicareMedical direction of two, three or four concurrent cases pays the physician 50 percent of the allowance for performing the case alone, and only when the physician performs the pre-anesthetic evaluation, prescribes the plan, personally participates in the most demanding parts including induction and emergence, ensures qualified individuals perform the rest, monitors at frequent intervals, remains physically present for emergencies and provides indicated post-anesthesia care. More than four concurrent cases, or other work while directing, drops the physician to three base units with one time unit if present at induction. Short emergencies nearby, labor epidurals and recovery room checks do not break direction; leaving the suite for more than a short time does.1
- MedicareNurse anesthetists report QX when medically directed and QZ when not, with QS available to either the physician or the nurse anesthetist for monitored anesthesia care as information only. A CRNA is identified on the provider file as specialty 43 and an anesthesiologist assistant as specialty 32, and when the employing physician takes assignment both services go on one claim as separate lines.1
- MedicareThe anesthesia base units by CPT code and the anesthesia conversion factors are posted on the Anesthesiologists Information Center, and CMS states that the base units are unchanged for CY 2026.2
- Medicare and plans that apply NCCIThe anesthesia package covers the preoperative evaluation, standard preparation and monitoring, administration, and post-anesthesia recovery care, and the routine postoperative evaluation is included in the base units. An epidural for postoperative pain is separately reportable with an anesthesia code only when the anesthetic was general and did not depend on the epidural; a peripheral nerve block only when the anesthetic was general, spinal or epidural and did not depend on the block. Neither is reportable when the anesthetic was monitored anesthesia care, moderate sedation or a regional block, and the surgeon must document the reason the pain management was referred.3
- MedicareContractors may not adjust fee schedule amounts for modifier 23, unusual anesthesia, or modifier 47, anesthesia by the surgeon, which puts both in the informational category on Medicare claims.1
Authorizations
Medicare has no separate authorization step for anesthesia; the anesthesia claim follows the coverage of the operation and is paid by the rules above. Where a commercial or Medicare Advantage plan ties the anesthesia claim to the surgeon's authorization, a missing authorization, or one issued for a different procedure code or site of service, takes the anesthesia line down with it. Your biller pulls the authorization from the facility or surgeon's schedule before the case, compares it to the code and site actually billed, and keeps each plan's own anesthesia payment policy on file next to its conversion factor.
Documentation traps
- An anesthesia record with a start time but no documented end, or times rounded to the quarter hour, so the minutes on the claim cannot be defended
- Medical direction without the record showing the pre-anesthetic examination, presence at induction and emergence, and the post-anesthesia care the physician provided
- Concurrency counted only for Medicare patients, when every room the physician was directing counts toward the two-to-four or more-than-four thresholds
- A nerve block for postoperative pain with no note from the surgeon requesting it and explaining why the surgeon could not manage the pain
- The physician and the CRNA both billing full rate for one case with documentation from only one of them
- Time around an interruption added to the total when continuous anesthesia care was not being furnished inside those blocks
What a specialist checks
Specialist or generalist for anesthesia billing?
A generalist biller can enter an anesthesia claim. Whether it pays turns on three things specific to anesthesia billing, and a specialty-aware biller checks each one.
Code families
Each family billed with what the chart has to show for it.
- 00100-01999
- 01996
- 36555, 93503, 31500
Modifiers
Applied only where the note supports them, line by line.
- AA
- QK
- QY and QX
If you are moving from another billing company or an in-house biller, switching billing companies follows a plan: the old and new processes run side by side until the new one is proven, and every login and every anesthesia claim stays in your name.
What we handle
What we handle for anesthesia practices
- Charge entryEvery encounter captured, nothing left unbilled
- Claim submissionScrubbed, submitted and tracked to acceptance
- Payment postingERAs and EOBs posted, variances flagged
- Denial managementEvery denial read, worked and appealed
- A/R follow-upUnpaid claims chased before filing limits
- CredentialingEnrollment, CAQH and PECOS kept current
A dedicated biller with named cover, working inside your system and reporting to you on one written page. How it works sets out the five stages.
Software
Systems anesthesia practices usually run
Your biller works inside your system as a user you create. All the systems we work in.
Questions
Questions about anesthesia billing
How is an anesthesia claim paid?
Medicare adds the base units for the anesthesia code to the time units, one for every 15 minutes rounded to a tenth, and multiplies the total by an anesthesia conversion factor for your locality. Medical direction halves the physician's allowance; supervision of more than four rooms caps the physician at three base units. A commercial plan pays by the terms of your contract with it.
When does anesthesia time start and stop?
It starts when the anesthesia practitioner begins preparing the patient for anesthesia in the operating room or an equivalent area, and it ends when the practitioner is no longer furnishing anesthesia services because the patient can be safely placed under postoperative care. It is one continuous period, except that blocks of time around an interruption can be added when continuous care was being given inside them. The pre-anesthesia exam and the routine recovery check are not time.
What is the difference between QK, QY, QX and QZ?
QK is the physician directing two to four concurrent cases. QY is the physician directing a single nurse anesthetist or anesthesiologist assistant. QX is the nurse anesthetist's line when a physician is directing. QZ is a CRNA working with no medical direction. The physician's and the anesthetist's modifiers have to agree with each other on the same case, and the two lines ordinarily carry the same minutes.
What happens when one anesthesiologist covers more than four rooms?
The service becomes medical supervision rather than direction. The physician reports AD and the contractor allows three base units for each case, with one time unit added if the record shows the physician was present at induction. The same cap applies when the physician is performing other services while directing four or fewer rooms.
Can we bill a nerve block for postoperative pain on the same day as the anesthesia?
Sometimes. The surgeon has to request the help and document why, and the mode of anesthesia matters: an epidural is reportable only when the operation was done under general anesthesia that did not depend on the epidural, and a peripheral block only when the operation was under general, spinal or epidural anesthesia that did not depend on the block. Under monitored anesthesia care, moderate sedation or a regional block there is no separate payment. When it qualifies, the block carries modifier 59 or XU.
How is monitored anesthesia care billed?
On the same basis as any other anesthesia service: base units plus actual minutes, at the personally performed rate when the physician does the case alone and at the medically directed rate when it is one of four or fewer directed rooms. QS is added to show it was monitored anesthesia care, and G8 or G9 where they apply, but each of those is informational and must sit next to one of the payment modifiers, never alone.
How do we bill when a CRNA and an anesthesiologist both work the whole case?
When both services are medically necessary and each practitioner documents why, the physician reports AA and the CRNA reports QZ, and the contractor can pay the full fee to each. The manual requires documentation from both providers to support the full fee to each, so a second full-rate line without it reads as a duplicate. This is a documentation decision made in the room, not a billing choice made afterward.
What does onboarding look like for an anesthesia group?
Your biller gets a user in your practice management system and clearinghouse under a signed BAA, plus a feed of the facility schedules and the anesthesia records your cases are built from. Your biller reconciles the schedule to the charges from the first case so unbilled cases surface, confirms every CRNA and assistant is enrolled and reassigned with each payer, and runs in parallel with your current process until the two agree.
Next step
See where your anesthesia claims are getting stuck.
Three quick questions. No patient data. A billing specialist reads every request and replies in writing.
- Three questions, about two minutes
- No patient data, no software to buy
- A written reply from a biller, not a sales deck
You answer three questions
A billing specialist reads them
A written reply by email
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Request received
Thanks. Your review request is in.
Reference . Quote it if you write to us about this request.
- A billing specialist reads your answers and replies by email.
- If a look at real claims makes sense, we agree read-only access under a BAA first.
- You get a written summary of what is worth working and what it would take. No commitment.
While you wait: see the sample weekly report or read how switching works. You can also download the sample weekly report (PDF).