Anesthesia Billing Services
Billing for anesthesiologists, CRNAs and anesthesia groups, built around base, time and modifying units, medical direction rules and clean time records. BilNow handles coding, claims and denials so your clinicians stay with patients.
98% First-Pass Claim Rate
Anesthesia Billing
Of Collections, No Setup Fee
No setup fee · No long-term contract · HIPAA-trained staff
Anesthesia Billing Services for Groups, CRNAs and Facilities
Anesthesia is paid on units, not a flat fee, so a wrong minute, modifier or staffing entry changes the payment. As an anesthesia billing company, BilNow runs anesthesia medical billing from coding to denials for these teams:
Anesthesiology Groups
Hospital and surgery-center groups with solo and medically directed cases, mixed Medicare, Medicaid and commercial contracts, and shared call coverage.
CRNA Groups and Independent CRNAs
Claims for CRNAs who work with or without medical direction, with QX or QZ on the correct lines and records that support each one.
Surgery Centers and Hospital Departments
Professional billing for facility-based anesthesia, with case data matched to the surgical schedule, the anesthesia record and the staffing log.
Pain and Regional Anesthesia
Post-operative blocks, epidural management and nerve blocks, billed as separate procedures only when the record supports them.
Endoscopy and Procedural Suites
Monitored anesthesia care billed with QS and the right payment modifier, plus G8 or G9 where the case qualifies.
Anesthesia Payment Formula: Base, Time and Modifying Units
Payment equals total units times a conversion factor. Total units are base units plus time units, plus any modifying units a payer recognizes. Each anesthesia code from 00100 to 01999 carries base units that reflect the work of the procedure, and the ASA Crosswalk lists the anesthesia code that most specifically describes each surgical CPT code. Medicare accepts one anesthesia code per case unless an add-on code applies.
| Part | How it is set | Billing note |
|---|---|---|
| Base units | Fixed for each anesthesia code | Chosen from the procedure performed, using the Crosswalk |
| Time units | Reported minutes divided by 15 | Medicare computes to one decimal place; some payers round |
| Modifying units | Physical status and qualifying circumstances | Paid by many commercial plans, not by Original Medicare |
| Conversion factor | Dollar value of one unit | Medicare sets it by locality; commercial rates follow your contract |
Take total knee arthroplasty (01402), which has 7 base units. A case of 129 minutes earns 8.6 time units, for 15.6 units before the conversion factor. ASA reports a 2026 Medicare anesthesia conversion factor of $20.4976 for clinicians outside a qualifying APM, and Medicare applies a locality-adjusted factor, so the same case pays differently by region.
Time reporting is where many claims are won or lost. Anesthesia time starts when the practitioner begins preparing the patient for anesthesia in the operating room or an equivalent area and ends when the practitioner is no longer furnishing anesthesia services. Claims report actual minutes, and the start and stop times on the claim must match the anesthesia record. Blocks of time around an interruption can be combined only when the record shows continuous care.
Medical Direction, Concurrency and Modifiers AA, QK, QY, QX, QZ and AD
Every anesthesia line needs a payment modifier that shows who did the work and how many cases the physician covered at once. The modifier sets the share of the allowance Medicare pays, so a wrong or missing one cuts payment or denies the claim. Our CPT modifiers cheat sheet explains AA, QK, QX, QY and QZ in plain English.
| Modifier | Meaning | Medicare payment |
|---|---|---|
| AA | Anesthesia personally performed by the anesthesiologist | Full allowance |
| QK | Medical direction of two, three or four concurrent procedures | 50% of the allowance |
| QY | Medical direction of one CRNA or anesthesiologist assistant | 50% of the allowance |
| QX | CRNA or anesthesiologist assistant service with medical direction | 50% of the allowance |
| QZ | CRNA service without medical direction | Full allowance |
| AD | Medical supervision of more than four concurrent procedures | Three base units per procedure, plus one time unit if the physician was present at induction |
Medical direction lets an anesthesiologist direct up to four concurrent cases, and Medicare requires a defined set of steps: the pre-anesthesia evaluation, the anesthesia plan, personal presence for the most demanding parts including induction and emergence, monitoring at frequent intervals, availability for emergencies and post-anesthesia care. The record must show at least the evaluation, the post-anesthesia care and presence at induction and emergence. A case with a resident adds GC.
Physical Status Modifiers P1-P6 and Qualifying Circumstances 99100-99140
Physical status modifiers record the ASA class of the patient: P1 normal healthy, P2 mild systemic disease, P3 severe systemic disease, P4 severe systemic disease that is a constant threat to life, P5 moribund and not expected to survive without the operation, and P6 a declared brain-dead organ donor. Payers that recognize them commonly add one unit for P3, two for P4 and three for P5, and none for P1, P2 or P6. The class on the claim must match the pre-anesthesia note.
Qualifying circumstances are add-on codes reported with the anesthesia code: 99100 for a patient younger than 1 year or older than 70 (1 unit), 99116 for total body hypothermia (5 units), 99135 for controlled hypotension (5 units) and 99140 for emergency conditions (2 units). Original Medicare pays nothing extra for P1-P6 or for these codes, while Medicare Advantage, Medicaid and commercial plans each set their own rule, so we load the rule for every payer.
Monitored Anesthesia Care and CRNA Billing: QS, G8, G9, QX and QZ
Monitored anesthesia care is billed with the anesthesia code for the procedure, the QS modifier and the payment modifier for the staffing model. G8 marks MAC for a deep, complex or markedly invasive procedure, and G9 marks MAC for a patient with a history of severe cardiopulmonary disease. Medicare treats QS, G8 and G9 as informational, so they do not change payment, but the record should still show why MAC was needed.
CRNAs bill with QX when an anesthesiologist directs the case and QZ when no physician directs it. A medically directed CRNA line is paid 50% of the allowance, and the directing physician's QY or QK line is paid 50% as well. Whether a CRNA may work without physician supervision depends on state rules and facility policy. Rural and critical access hospitals can be paid for CRNA services on a reasonable-cost pass-through basis, and those CRNAs do not bill the fee schedule.
Post-Operative Pain Blocks: Separate Billing With Modifier 59 or XU
A block placed for post-operative pain can be billed on top of the anesthesia claim, but only when the block is not the anesthetic for the surgery. An epidural (62320-62327) is separately reportable when the surgery is under general anesthesia and the adequacy of that anesthesia does not depend on the epidural. A peripheral nerve block (64400-64530) qualifies when the surgery is under general anesthesia, a subarachnoid injection or an epidural and does not depend on the block.
Modifier 59 or XU shows the block was for post-operative pain management. The record needs a separate procedure note, the surgeon's request for pain control and a diagnosis such as G89.18, acute post-procedural pain. A catheter that serves both surgery and recovery is part of the anesthesia code, and daily management (01996) is billed only on later days, one unit per day. For pain care outside the operating room, see our pain management billing services.
Common Anesthesia Denials and How We Prevent Them
Most anesthesia denials come from a short list of causes, and each can be checked before submission.
Time mismatches
Start and stop times that differ between the anesthesia record and the claim, or rounding that varies by provider. We reconcile minutes to the record before billing.
Wrong or missing payment modifier
AA, QK, QY, QX or QZ that does not match who did the work, or a CRNA line with no modifier. We check each claim against the staffing log.
Medical direction not documented
Directed cases without the pre-anesthesia evaluation or the induction and emergence entries lose the directed rate. We flag the gaps first.
Concurrency over the limit
More than four overlapping cases moves a physician to AD and three base units per case. We check overlap on the case log.
Units the payer does not pay
P3-P5 or qualifying circumstances billed to Original Medicare or to plans that bundle them. We set the rule for each payer.
Blocks billed with the anesthetic
Post-operative blocks sent without 59 or XU, a surgeon request or a procedure note. We hold them until the documentation is complete.
When a denial arrives, our denial management services team works the appeal, and our timely filing limits guide shows each payer's deadline so no claim ages out.
Credentialing, Payer Contracts and Pricing at 2.7% of Collections
Clean claims start with enrollment. Our medical credentialing services prepare applications for anesthesiologists and CRNAs, whether they bill under a group number or their own NPI. When a payer requires approval for the surgical or pain procedure, our prior authorization services track it so the anesthesia claim is not held up.
The No Surprises Act also shapes anesthesia revenue. Out-of-network anesthesiologists at in-network facilities generally cannot balance bill patients, who pay in-network cost sharing, so we track each payer payment against the rate you expect.
BilNow charges 2.7% of collections. There is no setup fee and no long-term contract, so the fee follows the money you collect. Our HIPAA-trained staff work inside your existing system, and we support more than 100 EHRs.
Anesthesia Billing FAQs
What are anesthesia billing services?
Anesthesia billing services cover coding, charge capture, claims, payment posting and denials for anesthesiologists, CRNAs and anesthesia groups. Payment depends on base units, time units, modifying units and a payer-specific conversion factor, so the work starts with the anesthesia record: times, staffing, physical status and procedure. BilNow turns that record into claims with the right code, modifier and units for each payer.
How is an anesthesia claim paid?
Payment is total units times the conversion factor. Total units are the base units for the anesthesia code, time units from reported minutes (one unit per 15 minutes, to one decimal place for Medicare) and any modifying units the payer recognizes. Medicare sets its conversion factor by locality, and commercial factors come from your contract. For example, 7 base units plus 129 minutes (8.6 time units) is 15.6 units.
What does the ASA Crosswalk do for anesthesia coding?
The ASA Crosswalk lists the anesthesia code, in the 00100-01999 range, that most specifically describes the service for a surgical or diagnostic CPT code, along with its base units. When no one-to-one match exists, it offers alternatives. Our coders use it to choose the anesthesia code from the procedure performed, so base units match the work and the claim agrees with the surgical record.
Which modifiers do anesthesia claims need?
Every line needs a payment modifier: AA for care the anesthesiologist performs personally, QK for directing two to four concurrent cases, QY for directing one CRNA, QX for a directed CRNA, QZ for a CRNA without direction and AD for supervising more than four cases. Physical status modifiers P1-P6, QS for monitored anesthesia care and GC for resident cases are added where they apply.
Are physical status modifiers and qualifying circumstances paid?
It depends on the payer. Original Medicare does not pay extra units for physical status modifiers or for qualifying circumstances codes 99100, 99116, 99135 and 99140. Many commercial payers do, commonly adding one unit for P3, two for P4 and three for P5. We set the rule for each payer, so units are claimed where paid and the ASA class is supported by the record.
Can a post-operative pain block be billed with the anesthesia?
Yes, when the block is for post-operative pain and the surgical anesthetic does not depend on it. The block is billed with its own CPT code (62320-62327 or 64400-64530) and modifier 59 or XU, supported by a separate procedure note and the surgeon's request. Without the modifier, the block may be rejected as part of the anesthetic. A block used as the surgical anesthetic is not billed separately.
Do you bill CRNA services and monitored anesthesia care?
Yes. CRNA lines carry QX or QZ depending on whether an anesthesiologist directed the case, and the directing physician's line carries QY or QK. Monitored anesthesia care is billed with QS, plus G8 or G9 where they apply. Hospitals paid for CRNA services on a pass-through basis do not bill the fee schedule, so we confirm how each site is paid before billing.
What does anesthesia billing cost with BilNow?
BilNow charges 2.7% of collections, with no setup fee and no long-term contract, so the cost follows the money you collect. Our HIPAA-trained staff handle coding, claims, payment posting and denials inside your existing system, and we support more than 100 EHRs. BilNow reports a 98% first-pass claim rate and a denial rate under 5%. Ask for a free review of your current billing before you decide.
Prepared by the BilNow Editorial Team · Last updated October 2, 2026
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