Anesthesia Billing Services: Time Units, Modifiers and Payment

Anesthesia Codes Our Team Bills Most

Modifiers That Matter

Payer Rules to Know

Top Denials in Anesthesia Billing Services: Time Units, Modifiers and Payment

How Is Anesthesia Paid with Base Units and Time Units?

Under the Medicare Physician Fee Schedule, anesthesia is paid as allowable base units plus allowable time units, multiplied by an anesthesia conversion factor specific to the locality. That is the general payment rule in the Medicare Claims Processing Manual, Chapter 12, section 50.

A base unit is a fixed value assigned to each anesthesia code for the work of the pre-anesthesia evaluation, the anesthetic and the usual monitoring. CMS sends them to the Medicare Administrative Contractors (MACs) in the annual HCPCS file, and its Anesthesiologists Center page says the 2026 base units are unchanged.

A time unit is 15 minutes of anesthesia time. You report actual minutes on the claim, and the MAC divides them by 15 and rounds to one decimal place. On the CMS-1500, Chapter 26 tells you to enter the elapsed time in minutes in item 24G and to convert hours into minutes.

Anesthesia time starts when the anesthesia practitioner begins preparing the patient in the operating room or an equivalent area. It ends when the practitioner is no longer furnishing anesthesia services and the patient can safely be placed under postoperative care. Chapter 12 treats it as one continuous period, though you can add blocks of time around an interruption.

What Is the 2026 Medicare Anesthesia Conversion Factor?

The 2026 national anesthesia conversion factor is $20.49754 for clinicians who are not Qualifying APM Participants and $20.599835 for those who are, both including the 2.5 percent statutory increase. These figures are in the ANES2026 file inside the CMS RVU26D release of the Physician Fee Schedule, updated 08/26/2026.

Each locality then applies its own geographic adjustment. In the 2026 file, the non-Qualifying APM conversion factor runs from $19.42 in Arkansas to $28.15 in Alaska. Manhattan is $22.81, Houston is $21.11 and Kentucky is $20.05.

The anesthesia codes carry status J in the Physician Fee Schedule relative value file. CMS defines J as anesthesia services with no RVUs and no payment amounts, so you cannot price an anesthesia claim from the usual RVU columns. Use the base unit file and the conversion factor file instead.

Commercial payers do not have to use CMS values. Ask for the contract conversion factor and base unit source in writing. The American Society of Anesthesiologists (ASA) publishes a Relative Value Guide with ASA base units and a Crosswalk that maps surgical CPT codes to anesthesia codes. Both are copyrighted ASA products, so we point you to them and do not reproduce their tables here.

What Do the Anesthesia Modifiers AA, QK, QX, QY and QZ Mean?

Each anesthesia line needs one payment modifier that tells the payer who performed the service and under what level of direction. Chapter 12 lists the physician modifiers in section 50I and the nonphysician anesthetist modifiers in section 140.3.3.

The pairs matter. When an anesthesiologist directs one CRNA on a single case, Chapter 12, section 140.4.2 says each is paid 50 percent of the allowance for the anesthesiologist working alone. The physician reports QY and the CRNA reports QX. The QK modifier replaces QY when the physician directs two, three or four cases at once. Where both the CRNA and the anesthesiologist are completely and fully involved and it is medically necessary, section 140.4.2 allows full payment to each, with AA and QZ, and both must submit documentation.

Other modifiers still apply on anesthesia claims. When an anesthesia practitioner reports a postoperative pain block or epidural on the same date as the anesthesia code, the NCCI manual says modifier 59 or XU may show the injection was for postoperative pain.

What Is the Difference Between Medical Direction and Supervision?

Medical direction pays the anesthesiologist at 50 percent of the personally performed allowance and requires seven specific activities for every case. Medical supervision (modifier AD) applies when the physician is over the limit of four concurrent cases or is performing other services while directing. Supervision pays far less. The rules are in Chapter 12, section 50, and 42 CFR 415.110.

Under 42 CFR 415.110(a), Medicare pays for the physician's medical direction of one service, or of two to four concurrent services, when the physician directs no more than four anesthesia services at once. For each patient the physician must do the following.

1. Perform a pre-anesthetic examination and evaluation.
2. Prescribe the anesthesia plan.
3. Personally participate in the most demanding procedures in the plan, including induction and emergence where applicable.
4. Make sure any part of the plan the physician does not perform is done by a qualified individual.
5. Monitor the course of anesthesia administration at frequent intervals.
6. Remain physically present and available for immediate diagnosis and treatment of emergencies.
7. Provide indicated post-anesthesia care.

Concurrency counts all the cases, not only Medicare ones. Chapter 12 gives the example of an anesthesiologist directing three procedures where two patients are not on Medicare: that is still three concurrent cases. A schedule that puts five rooms under one physician quietly turns QK lines into AD lines.

Chapter 12 allows some activity without breaking medical direction. Examples are a short emergency in the immediate area, an epidural for labor pain, periodic monitoring of an obstetrical patient and checking patients in recovery. Leaving the operating suite area for more than short periods, or devoting extensive time to an emergency case, means the case does not meet the medically directed requirements.

When more than four cases overlap, Chapter 12 allows only three base units per procedure. One more time unit is recognized if the physician documents presence at induction.

How Do We Bill a CRNA Under Medical Direction?

A CRNA bills with modifier QX when a physician medically directs the case and QZ when the CRNA works without medical direction. Payment goes to the CRNA, or to the employer or contracting entity such as a hospital, physician group or ambulatory surgical center, as Chapter 12, section 140.2 allows.

A certified registered nurse anesthetist (CRNA) is a licensed registered nurse who graduated from an accredited nurse anesthesia program and is certified. An anesthesiologist assistant always works under an anesthesiologist. Medicare calls both qualified nonphysician anesthetists (42 CFR 410.69; Chapter 12, section 140.1).

For a medically directed case, both lines carry the same base units and the same time. The directing physician ordinarily reports the same time as the qualified nonphysician anesthetist, according to section 50G. That is why mismatched start and stop times between the two claims cause review requests.

What Is Already Included in the Anesthesia Code and What Can You Bill Separately?

The anesthesia code includes the preoperative evaluation, standard preparation and monitoring, administration of the anesthetic and the usual recovery care until the patient is released. The 2026 NCCI Policy Manual, Chapter II, says airway placement, peripheral IV lines, laryngoscopy, and routine monitoring set-up are all integral and not separately reportable with the anesthesia code.

A few things stay billable. The NCCI manual allows an evaluation and management code when surgery is canceled after the preoperative evaluation. It also allows separately reportable services such as central venous pressure line insertion, a Swan-Ganz catheter and emergency intubation outside the operating suite, when state licensing laws allow.

Postoperative pain follows the global surgery rule. The surgeon is responsible for postoperative pain management and cannot bill it separately, but the surgeon may request help from anesthesia. An epidural injection for postoperative pain may be reported with an anesthesia code only if the intraoperative anesthetic is general and does not depend on the epidural. A peripheral nerve block may be reported only with general, subarachnoid or epidural anesthesia, and modifier 59 or XU shows it was for postoperative pain.

Daily management of epidural or subarachnoid drug administration (CPT 01996) is not paid on the date the catheter is placed. It is paid for later days, limited to one unit per day.

Medicare does not allow separate payment for anesthesia furnished by the same physician who performs the surgery or procedure, with limited exceptions. An anesthesia line billed under the operating surgeon's NPI is therefore at risk of denial. NCCI procedure-to-procedure and medically unlikely edits apply to anesthesia as they do elsewhere.

For several surgeries in one session, Chapter 12, section 50E tells you to report the anesthesia code with the highest base unit value, with modifier 51, and put the total time for all procedures on that line. When the same anesthesia code covers several surgeries, enter the code once with the number of surgeries. Commercial policies differ.

Does the No Surprises Act Protect Patients Seen by an Out-of-Network Anesthesiologist?

Yes, for patients with group health plan or group or individual health insurance coverage. An anesthesiologist who is out of network for a patient's plan but works at an in-network hospital cannot balance bill that patient beyond the in-network cost-sharing amount. Under 45 CFR 149.420(b), notice and consent never applies to items and services related to anesthesiology, whether provided by a physician or a nonphysician practitioner. The notice and consent page has the full rule.

The patient cannot sign a waiver to be billed the difference, and a CRNA is covered the same way. The payment fight moves from the patient to the plan. You send the claim to the plan, take the plan's initial payment or denial and, if the amount is too low, use open negotiation and then the federal IDR process, where the plan's qualifying payment amount is one of the figures considered.

Anesthesia disputes have a feature of their own. The claim has a base unit component and a time component, and a payer's initial payment can underpay by using a wrong conversion factor or a wrong time interval. Before negotiating, recompute the expected payment and confirm the payer processed the same minutes and modifier. Our out-of-network billing and IDR service covers the full workflow.

Why Do Anesthesia Claims Deny When the Surgery Claim Is Denied?

Payers adjudicate anesthesia against the procedure it supports. If the surgeon's claim denies for medical necessity (CARC 50) or absent authorization (CARC 197), the related anesthesia line often follows.

Fix this at the source: confirm the surgical authorization number before the date of service and put the same diagnosis on both claims. Endoscopy cases (see gastroenterology billing) and sedation for imaging (see radiology billing) are common examples. Link the correct surgical code to the anesthesia code using the ASA Crosswalk. If the procedure denial is overturned on appeal, resubmit or appeal the anesthesia line with the surgical decision attached.

How We Handle Anesthesia Billing

We code and bill anesthesia from the anesthesia record, not from a charge slip. Our AAPC and AHIMA certified coders read the start and stop times, the staffing roster and the surgical procedure, pick the anesthesia code and set the payment modifier. A mismatch between the roster and the modifier is fixed before the claim goes out.

Claims leave within 24 hours of charge entry, and denials are worked within 48 hours. For hospital-based and facility-based groups we reconcile minutes between the anesthesiologist and CRNA lines so a medically directed pair matches, we check concurrency against the schedule, and we run medical coding review on the surgical code that drives the anesthesia code.

Out-of-network anesthesia claims go through eligibility assessment, open negotiation and federal IDR or the applicable state process, with deadline tracking and documentation checks at each step. Our team works inside your EHR and your payer portals. If you want us to look at how your anesthesia claims are paid today, book a call.