Assistant surgeon pay: 16 percent, and sometimes none.

The indicator

The Assistant at Surgery field (modifiers AS, 80, 81 and 82) is at position 37 of the payment policy indicator file (Chapter 23, section 50.6); Chapter 12 calls it Field 23. Its values: 0, the restriction applies unless supporting documentation establishes medical necessity; 1, a statutory restriction applies and an assistant may not be paid; 2, the restriction does not apply and an assistant may be paid; 9, the concept does not apply.

The rates

For assistant-at-surgery services performed by physicians, the fee schedule amount is 16 percent of the amount otherwise applicable for the surgical payment (Chapter 12, section 20.4.3). Physician assistants, nurse practitioners and clinical nurse specialists are paid at 80 percent of the lesser of the actual charge or 85 percent of what a physician is paid (sections 110.2 and 120.1). Because the physician rate is 16 percent of the surgical amount, the manual states the result as 13.6 percent. That is 85 percent of 16 percent, and it is the basis the calculator uses for the AS modifier; the 80 percent payment share and cost sharing are not applied.

Which modifiers

Procedures billed with the physician assistant-at-surgery modifiers 80, 81 or 82, or with AS for physician assistants, nurse practitioners and clinical nurse specialists, are subject to the policy. Claims are paid only where an assistant is authorized for the procedure. Contractors also may not pay assistants for procedures where a physician assistant at surgery is used in fewer than five percent of cases nationally (Chapter 12, section 20.4.3).

When the patient can be billed

For a procedure under the statutory restriction, payment is denied with group code CO and CARC 54, and the manual instructs contractors to tell the patient "You cannot be charged for this service." (Chapter 12, section 40.8.D). For indicator 0, limitation on liability provisions apply to assigned claims. Medicare's rules against billing patients above the allowed amount apply to assistant-at-surgery services, and knowing and willful violations can bring penalties.

Worked example (hypothetical)

If the surgical fee schedule amount is $2,000 and the indicator is 2, an assistant-surgeon physician has a fee schedule amount of $320 (16 percent). A PA, NP or CNS has $272 (13.6 percent) before the 80 percent payment share. With indicator 1 the answer is zero for both.

Where the row wording needed correcting

The search phrase pairs the modifiers with "16/85 percent". Sixteen percent is the physician rate. The 85 percent figure is the factor for PAs, NPs and CNSs, not a second rate for physicians.

FAQ

How much does Medicare pay an assistant surgeon?

For physicians, the fee schedule amount is 16 percent of the amount otherwise applicable for the surgical payment.

What is the 85 percent in assistant-at-surgery payment?

It applies to physician assistants, nurse practitioners and clinical nurse specialists, who are paid at 80 percent of the lesser of the actual charge or 85 percent of what a physician is paid. The manual puts the result at 13.6 percent.

What does assistant at surgery indicator 1 mean?

A statutory payment restriction applies and an assistant at surgery may not be paid for that procedure.

Which modifiers does the policy cover?

Modifiers 80, 81 and 82 for physicians, and AS for physician assistants, nurse practitioners and clinical nurse specialists.

Can the patient be billed when payment is denied under the statutory restriction?

CMS instructs contractors to give the message "You cannot be charged for this service." and the denial carries group code CO, so the provider is liable.

Sources

Retrieved 2026-11-02 from the CMS documents below. Indicator meanings are paraphrased from the CMS definitions; no AMA CPT descriptors are reproduced. CMS revises the fee schedule and its manuals, so check the current text.

• CMS: Medicare Claims Processing Manual, Chapter 12, Physicians/Nonphysician Practitioners (Rev. 13753, issued 05-07-26): sections 20.4.3, 40.8.D, 110.2 and 120.1 (retrieved 2026-11-02).
• CMS: Medicare Claims Processing Manual, Chapter 23, Fee Schedule Administration and Coding Requirements (Rev. 13701, issued 06-16-26): section 50.6, Assistant at Surgery field (retrieved 2026-11-02).
• CMS: MLN907166, Global Surgery booklet (December 2025): Assistant-at-Surgery Services (retrieved 2026-11-02).