How to bill for anaesthetic services — the complete guide for Australian anaesthetists in private practice.
Private anaesthetic billing is its own discipline. Base units, time units, ASA modifiers, MBS items and Informed Financial Consent all have to line up before the claim leaves your desk — and the rules aren't taught at the registrar level. This guide walks through every component, in the order you actually use them, with a live fee calculator you can use for real cases.
takeaways
Fees are unit-based. Base units + time units + ASA modifier + other modifiers, multiplied by your per-unit dollar rate.
Time units: 1 per 15 min for the first 2 hours, then 1 per 10 min thereafter — from start of exclusive care to PACU handover.
ASA 3 adds one unit, ASA 4 adds two, ASA 5 adds three. ASA 1 and 2 add nothing — document your reason.
Get the surgeon's MBS item in writing. Reusing the previous case's number is the #1 billing error.
IFC is required by the Medical Board's Code of Conduct (s. 4.5.3) — ideally in writing, at least two business days before the procedure.
Outsource above ~2 lists/week. Self-bill below that, professional service above — the maths is straightforward.
How an anaesthetic fee is actually calculated.
Anaesthetic billing in Australia uses a relative value system. Every fee is built from four ingredients, then multiplied by a per-unit dollar value set by your fee schedule (typically $60–$100 per unit, depending on location and your health-fund agreements).
- Base units — assigned to each surgical procedure under the MBS
- Time units — one for every 15 minutes of anaesthesia for the first 2 hours, then one for every 10 minutes thereafter
- Physical status modifier — +1 for ASA 3 (item 25000), +2 for ASA 4 (item 25005), +3 for ASA 5 (item 25010)
- Age modifier — +1 unit for patients under 4 (item 25013) or aged 75+ (item 25014)
- Emergency modifiers — +2 units for in-hours emergency (item 25020), or a 50% fee loading for after-hours emergency (item 25025). The two are mutually exclusive.
- Pre-anaesthesia consult — item 17610 (≤15 min, +2 RVG units) or 17615 (15–30 min, +4 RVG units). Charged at units × per-unit rate, but listed separately on the invoice and not subject to the after-hours loading.
This is the Relative Value Guide (RVG) approach — the same model used by the ASA in the United States, adapted for the Australian MBS. Most rejections come from one of these components being wrong.
From the MBS schedule for the surgical item number.
From start of exclusive care to PACU handover. 1 unit per 15 min for the first 2 hrs, then 1 unit per 10 min.
Item 25000 (ASA 3) · 25005 (ASA 4) · 25010 (ASA 5).
Saved to your browser for next visit.
Item 25013 (under 4) or 25014 (75+).
Items 25020 (in-hours, +2 units) or 25025 (after-hours, 50% fee loading on subtotal). Mutually exclusive — only one applies. The MBS after-hours window is 8pm–8am on weekdays, plus all of Saturday, Sunday and public holidays, with more than 50% of the anaesthetic time falling within that window.
Consult priced at units × your per-unit rate. Not subject to the after-hours loading.
ASA scores in anaesthesia and when they add billing units.
ASA scores classify the patient's preoperative physical status. Only ASA 3 and above add billing units — but the classification has to be defensible in your record, because health funds increasingly request supporting notes.
Worked case: A 67-year-old with obstructive sleep apnoea, type 2 diabetes and hypertension presenting for total hip replacement is appropriately ASA 3, provided those comorbidities materially affect perioperative risk — and provided that's stated in your record.
Anaesthesia time units — start to handover.
Anaesthesia time has its own set of MBS rules, and they're not what most registrars assume. Per the MBS Note TN.10.1, time is measured by two formulas depending on case length, and the start and end points are tightly defined.
The two-tier rule
- First 2 hours: 1 time unit per 15 minutes (or part thereof)
- Beyond 2 hours: 1 time unit per 10 minutes (or part thereof)
So a 3-hour case isn't 12 units — it's 14 (8 units for the first 2 hours, then 6 more for the remaining 60 minutes at 1/10). A 5-hour case isn't 20 units — it's 26 (item 23220). Calculators that use a flat 1/15 rule silently underbill every case longer than 2 hours.
When time starts and ends
Per MBS, anaesthesia time begins when the anaesthetist commences exclusive and continuous care of the patient, and ends when the patient is safely placed under the supervision of other personnel. In practical terms, that's:
- Pre-oxygenation, induction, line placement and regional blocks performed by you
- The surgical anaesthetic itself
- Emergence from anaesthesia
- PACU handover until clinical responsibility transfers to recovery staff
The most common time-unit error is under-recording — particularly the pre-induction and handover windows. Both are billable, both are routinely missed, and across a year that's a meaningful number of units left uncounted.
Choosing the right MBS item number for the procedure.
Each surgical procedure maps to a corresponding anaesthetic item number under the Medicare Benefits Schedule, which determines your base unit count. Get the item wrong and the whole calculation is wrong — even if your time and ASA were correct.
The two-step rule
- Get the surgeon's MBS item number for the operation, in writing where possible
- Match it to the corresponding anaesthetic item number from the MBS schedule
The pitfall almost everyone falls into early in private practice is reusing the previous case's item number because the surgeries look similar. They're often not. A laparoscopic cholecystectomy and an open cholecystectomy attract different anaesthetic items, even though both target the gallbladder — the difficulty (and therefore the base unit value) is materially different. If you're not certain, ask the surgeon's room before the list, not after the fact.
Informed Financial Consent for anaesthetists — required by the Code of Conduct.
Informed Financial Consent (IFC) is a binding professional requirement for every registered medical practitioner in Australia. The Medical Board of Australia's Good Medical Practice: A Code of Conduct for Doctors mandates this directly at section 4.5.3: doctors must "ensure that your patients are informed about your fees and charges in a timely manner to enable them to make an informed decision about whether they want to proceed." The Code is issued under the Health Practitioner Regulation National Law Act 2009 and is enforceable; breaches can result in AHPRA disciplinary action ranging from conditions on registration through to suspension or deregistration. The requirement is reinforced by sections 4.5.4 (additional-costs disclosure when referring), 4.2.6 (no financial exploitation), and 8.12.5 (financial transparency), and by ASA Position Statement PS04 and the AMA Guide to Informed Financial Consent. Beyond compliance, IFC is the single most important thing standing between you and a billing complaint.
What an IFC should cover
- The estimated total fee for the procedure (a range is acceptable per ASA PS04)
- Any expected out-of-pocket cost to the patient, with a disclaimer that fund rebates should be confirmed by the patient with their fund
- Whether the practitioner participates in any "no-gap" or "known-gap" scheme with the patient's fund
- How the fee may change if the procedure runs longer or shorter than expected
The gold standard is a written estimate — per ASA PS04, IFC can be verbal or written, but a written record (email is acceptable) is what stands up under scrutiny if a complaint is later lodged. The recommended timing is at least two business days before the procedure, so the patient has time to review, query and prepare. Patients almost never object to a fee they were warned about. They almost always object to a fee that surprised them.
Common billing mistakes anaesthetists make — and what they actually cost.
Across 200,000+ anaesthetic invoices we've processed, six errors come up again and again. None of them are dramatic in isolation. All of them, repeated weekly, cost a private anaesthetist five figures a year.
Reusing the previous case's item number
Two patients on the same list, two different procedures, one item number copied from the first to the second. The under- or over-claim is invisible until the rejection comes back weeks later.
Forgetting the ASA 3 or 4 modifier
The patient was clearly ASA 3 in your record. The modifier never made it onto the claim. Roughly 15% of the ASA 3 work we audit on intake has been billed at ASA 1 or 2 by the previous biller.
Under-recording time
Pre-induction and PACU handover are routinely missed. Across a list of six cases, that can easily be 20+ minutes of billable time discarded — one to two units' worth, every list.
Skipping IFC for "small" gaps
If there's any out-of-pocket cost — even $50 — the patient needs IFC in writing in advance. Skipping it doesn't just expose you to complaints; it exposes you to refund obligations.
Billing the fund without checking coverage
Submitting to a fund the patient doesn't actually hold cover with creates a rejected claim, a delayed payment, and an awkward call to the patient. Five seconds of pre-list verification prevents weeks of follow-up.
Not following up rejections
The single most expensive mistake. Roughly 1 in 7 anaesthetic claims comes back with some form of query or downcode. Practitioners who don't appeal those leave 8–12% of revenue on the table over a year.
Billing in public versus private settings.
Anaesthetic billing rules are different depending on where the case is performed and how the patient is admitted — and this is one of the trickier areas for anaesthetists who split their week.
Public hospitals
Standard public-hospital cases generally aren't separately billable — you're paid through your VMO contract or salary. The exception is a privately admitted patient in a public hospital, where billing is permitted and expected, provided the patient was formally booked as private with their own cover.
Private hospitals
You must provide IFC. You bill either the fund (under no-gap or known-gap arrangements), Medicare directly, or the patient — depending on the scheme you've signed up to. If you've registered with health-fund schemes, you're bound by their out-of-pocket caps and rules; many anaesthetists don't realise they've inadvertently breached a no-gap rule by charging a higher fee than the scheme allows.
Mixed environments
The most common error in mixed work is billing a public-admitted patient privately. Always confirm admission status before lodging anything — the hospital admissions office is the source of truth, not the theatre list.
Should you do your own anaesthetic billing — or delegate it?
The honest answer is that it depends on volume. If you bill fewer than two private cases a week, doing it yourself is fine — the maths is straightforward and the time investment is minimal.
Beyond that point, the calculation changes. The mistakes outlined above don't show up as missing money — they show up as rejected claims, downcodes and quiet under-billing that compound silently. Most anaesthetists who switch to a professional billing service from in-house find the service pays for itself within the first two months on rejection recovery and modifier capture alone.
A professional anaesthetic billing service handles:
- Correct MBS item selection for every case
- Time-unit and modifier capture
- IFC drafting, sending and storage
- Claim lodgement to Medicare, funds and DVA
- Active appeals on rejections and downcodes
- Patient invoicing, follow-up and reconciliation
- Monthly reporting for BAS, tax and forecasting
Frequently asked questions about anaesthetic billing.
How is the anaesthetic Relative Value Guide (RVG) calculated?
The RVG fee is built from four components: base units (assigned per surgical procedure), time units (one per 15 minutes for the first 2 hours, then one per 10 minutes thereafter, rounded up), physical status modifiers (+1 for ASA 3, +2 for ASA 4, +3 for ASA 5), and other modifiers — +1 for patients under 4 or aged 75+, +2 units for in-hours emergency, or a 50% fee loading for after-hours emergency (mutually exclusive). The total unit count is multiplied by the per-unit dollar value set by your fee schedule. Try the calculator above to work out a specific case.
How much does anaesthesia cost per minute in Australia?
Anaesthesia is billed in time units, not minutes — and the rate steps up after 2 hours. For the first 2 hours, you get one unit per 15 minutes, so at $60–$100 per unit that's roughly $4–$7 per minute. Beyond 2 hours the rate becomes one unit per 10 minutes, so the per-minute cost rises to $6–$10 per minute. Base units add a separate $300–$500+ on top of time, regardless of how long the procedure takes.
What is the difference between ASA 3 and ASA 4?
ASA 3 is a patient with severe systemic disease that limits activity but is not incapacitating — controlled diabetes with end-organ effects, COPD, severe obesity. ASA 4 is severe systemic disease that is a constant threat to life — recent MI, ongoing cardiac ischaemia, severe respiratory failure. ASA 3 adds one billing unit (item 25000); ASA 4 adds two (item 25005). ASA 5 (moribund, not expected to survive 24 hours) adds three (item 25010).
Is Informed Financial Consent legally required for anaesthetists?
Yes — in effect. The Medical Board of Australia's Good Medical Practice: A Code of Conduct for Doctors directly requires it at section 4.5.3: doctors must ensure patients are informed about fees and charges in a timely manner to make an informed decision about whether to proceed. The Code is issued under the Health Practitioner Regulation National Law and binds every registered medical practitioner in Australia — breaches can result in AHPRA disciplinary action up to and including suspension or deregistration. ASA Position Statement PS04 and the AMA's IFC guide reinforce this. The gold standard is a written IFC issued at least two business days before the procedure.
What MBS item number do I use for anaesthesia?
There isn't one anaesthesia item number — there are hundreds. Each surgical procedure has a corresponding anaesthetic MBS item with its own base-unit count. Get the surgical item number from the surgeon's rooms in writing, then match it to the corresponding anaesthetic item in the MBS schedule. Don't reuse the previous case's number even if the surgeries look similar.
What's the most common billing mistake anaesthetists make?
Using the wrong anaesthetic item number for the surgical procedure — usually because the previous case's code was reused without checking. The next most common is omitting the ASA 3 or 4 modifier when it would have been clinically justified. Both are silent revenue losses; neither generates an obvious rejection.
Can I bill a patient privately in a public hospital?
Only if the patient was formally admitted as a private patient with their own private health cover or election. Patients in public beds under the public system aren't billable, even if the surgery is identical. The hospital's admissions office is the source of truth on admission status — not the theatre list.
How long does it take to learn anaesthetic billing properly?
The mechanics — base units plus time plus ASA — can be picked up in an afternoon. The hard part is the long tail: which items pair with which procedures, which fund schemes you're signed up to and what their no-gap caps are, how to write an appeal that gets a downcode reversed, and what to actually say in an IFC. That nuance takes most anaesthetists two to three years of full private practice to internalise.
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