Modifier 80: Assistant Surgeon Payment Rules
Modifier 80 bills an assisting surgeon. Medicare pays 16% of the surgery's fee schedule amount for approved codes. Indicators, rules and 80 vs 82 vs AS.
Modifier 80 is a billing modifier that a physician adds to the surgical code when they assisted the primary surgeon throughout an operation. Medicare pays the assistant 16% of the fee schedule amount for the surgery (Pub. 100-04, ch. 12, §20.4.3), but only for procedures where the fee schedule allows an assistant at surgery.
Key takeaways
- Payment is 16% of the surgical fee schedule amount.
- Check the procedure's assistant-at-surgery indicator first: 2 means payable, 0 needs documentation of medical necessity, 1 means never paid.
- Medicare doesn't pay an assistant for procedures where physicians assist in fewer than 5% of cases nationally.
- In a teaching hospital with a qualified resident available, Medicare won't pay an assistant. Use 82 when no qualified resident was available.
- Physician assistants, NPs and CNSs use AS, not 80.
Modifier 80 · payment effect
With and without the modifier
27447 without 80 · national facility
$1,159.35
Total knee replacement
27447-80 · Assistant: 16%
$185.50
A physician assistant at surgery is paid 16% of the surgeon’s fee schedule amount.
When to use modifier 80
Use 80 when:
- A physician actively assisted the primary surgeon for the whole procedure, not just part of it or for ancillary tasks.
- The procedure's assistant-at-surgery indicator allows it.
The indicator is published in the fee schedule for every code and shown on FeeBase code pages.
CMS payment indicators · 27447
Total knee replacement
| Rule | CMS value | What it means |
|---|---|---|
| Global period | 090 | Major surgery: the day before, the day of, and 90 days after are included. |
| Multiple procedures | 2 | Standard reduction: highest-valued procedure at 100%, others at 50%. |
| Bilateral (modifier 50) | 1 | Bilateral with modifier 50 pays 150% of the fee schedule amount. |
| Assistant at surgery (80/81/82/AS) | 2 | Paid. |
| Co-surgeons (62) | 1 | Permitted with supporting documentation. |
| Team surgery (66) | 0 | Not permitted. |
| Professional/technical | 0 | Physician service: no professional/technical split. |
| Split (54/55/56) | 0.10/0.69/0.21 | Share of the payment for pre-op, the procedure itself, and post-op care. |
| Indicator | What it means for 80, 81, 82 and AS |
|---|---|
| 0 | Paid only with documentation that an assistant was medically necessary |
| 1 | Statutory restriction: an assistant is never paid |
| 2 | An assistant at surgery may be paid |
| 9 | The concept doesn't apply to this code |
Example. An orthopedic surgeon performs a total knee replacement (27447, indicator 2) with a second orthopedic surgeon assisting. The primary surgeon bills 27447; the assistant bills 27447-80 and is paid 16% of the fee schedule amount. For a knee arthroscopy with meniscectomy (29881, indicator 0), the assistant's claim needs a note explaining why an assistant was necessary.
When not to use modifier 80
- Teaching hospitals with a qualified resident available in a training program for that specialty. Medicare doesn't pay assistants there (ch. 12, §100.1.7). If no qualified resident was available, use 82 and the required certification.
- Two surgeons each performing a distinct part of the procedure. That is co-surgery, modifier 62, not 80.
- Non-physician assistants. PAs, NPs and CNSs use AS.
- The assistant furnished only ancillary services rather than actively assisting.
How modifier 80 affects payment
The assistant's allowed amount is 16% of the fee schedule amount for the surgery (ch. 12, §20.4.3). When the primary surgeon bills several procedures, the assistant bills the same codes with 80 and the multiple-procedure ranking applies to the assistant's lines too (modifier 51). The surgeon's own payment is unaffected by the assistant's claim.
Medicare pays assistant claims only when an assistant is authorized for the code, and doesn't pay assistants for procedures where a physician assists in fewer than 5% of cases nationally.
Modifier 80 vs 81, 82, AS and 62
| Modifier | Who | Payment |
|---|---|---|
| 80 | Physician assisting for the whole procedure | 16% of the surgical fee schedule amount |
| 81 | Physician providing minimal assistance | 16%, under the same assistant rules |
| 82 | Physician assisting in a teaching hospital when no qualified resident was available | 16%, with certification |
| AS | PA, NP or CNS assisting | 85% of the physician's 16% (13.6% of the surgical amount) |
| 62 | Two co-surgeons each performing a distinct part | 62.5% of the global surgery amount each |
FAQ
What is the difference between modifier 62 and 80?
62 is for co-surgeons: two surgeons who each perform a distinct part of one procedure, each paid 62.5% of the global surgery amount. 80 is for an assistant who helps the primary surgeon, paid 16%.
What is the difference between modifiers 80 and 81?
80 is for an assistant present for the whole procedure. 81 is for minimal assistance. Medicare processes both under the same assistant-at-surgery rules and payment rate.
How much does Medicare pay an assistant surgeon?
16% of the fee schedule amount for the surgery when the assistant is a physician, and 85% of that (13.6% of the surgical amount) when the assistant is a PA, NP or CNS billing with AS.
What is an 80 modifier used for?
To bill the services of a physician who assisted the primary surgeon during a procedure where Medicare allows an assistant at surgery.
Can a physician assistant bill modifier 80?
No. CMS requires the AS modifier for assistant-at-surgery services by PAs, NPs and CNSs.
Keep reading
- Modifier AS for PA, NP and CNS assistants.
- Modifier 62 for co-surgery and modifier 51 for multiple procedures.
- Global period calculator for the surgery's postoperative window.
- Codes on this page: 27447 29881 64721 43846
Sources: CMS Medicare Claims Processing Manual, Pub. 100-04, ch. 12, §§20.4.3, 40.8, 100.1.7, 110.2 and 120.1; CMS PFS relative value file assistant-at-surgery indicators; Noridian JF Part B, Modifier 80 (updated May 12, 2025). Verified October 6, 2026.
