Assigning Assistant Surgeon Modifiers

When reviewing operative reports involving participation by multiple providers, it is very important to determine which part(s) of the procedure each provider is involved in performing. Is there an additional provider assisting the primary provider? If so, the coder will need to determine if an assistant surgeon modifier should be assigned to ensure that all providers are appropriately reimbursed for their services.

What is assistance at surgery?

An assistant surgeon is a physician who actively assists the physician in charge of a case in performing a surgical procedure. (Note that a nurse practitioner, physician assistant or clinical nurse specialist who is authorized to provide such services under State law can also serve as an assistant at surgery). The conditions for coverage of such services in teaching hospitals are more restrictive than those in other settings because of the availability of residents at a teaching hospital who are qualified to perform this type of service.

What modifiers are available to indicate assistance at surgery?

There are multiple modifiers to report a provider’s assistance in performing a procedure. The modifier assigned depends upon the type of provider assisting and the circumstances.

Assistant at Surgery Modifiers
Modifier Definition
–80 Assistant Surgeon – Assistant at surgery services are provided by a physician. The assistant surgeon is present during the entire operation or a substantial portion of the operation to provide assistance to the operating physician.
–81 Minimum Assistant Surgeon Assistant at surgery services are provided by a physician. A minor problem is encountered during the operation that requires the service of an assistant surgeon for a relatively short period of time.
–82 Assistant Surgeon (when qualified resident surgeon not available) Assistant at surgery services provided by a physician in a teaching hospital when a qualified resident surgeon is not available. • The unavailability of a qualified resident surgeon must be documented in the medical record.
–AS Physician assistant, nurse practitioner, or clinical nurse specialist services for assistant at surgery Physician assistant, nurse practitioner or clinical nurse specialist services who participated as an assistant to a surgeon.


Correct reimbursement is dependent on a clear understanding that modifier -80, -81 and -82 should not be used when billing for services provided by non-physician providers such as physician assistants, nurse practitioners and clinical nurse specialists. Medicare has created HCPCS modifier -AS for use by non-physician providers who are eligible for reimbursement for assistant at surgery services. Additionally, professionals such as certified surgical assistants (CSA) are not eligible for reimbursement for assistant at surgery services, so none of these modifiers should be used by these clinicians.

How does the coder know if a modifier is allowed?

Whether or not a modifier is allowed for use with a specific CPT may be regulated by payment policy or it may be regulated by circumstances. There are many tools and resources a coder can use to determine if an Assistant Surgeon or other modifier is allowed with a specific CPT code. These are discussed below.

Regulation by policy

Medicare has several payment policy indicators related to CPT codes. One of those is a status indicator that signals whether it is permissible to append certain modifiers to CPT code. Before assigning Assistant Surgeon modifiers, the coder should check the Assistant Surgeon modifier’s status indicator associated with the CPT code they intend to assign. The status indicator tells the coder whether appending a particular modifier to a particular CPT code is allowed.

Status Indicators for Modifiers
Indicator Definition
0 Payment restrictions for assistants at surgery applies to this procedure unless supporting documentation is submitted to establish medical necessity. Supporting documentation must be submitted at the time of claim submission to established medical necessity and should clearly document the assistant surgeon's role during the operative session.
1 Statutory payment restriction for assistants at surgery applies to this procedure. Assistant at surgery may not be paid.
2 Payment restrictions for assistants at surgery does not apply to this procedure. Assistant at surgery may be paid.
9 The concept of assistance at surgery does not apply.


Status indicators for Assistant Surgeon modifiers are found in the Medicare Physician Fee Schedule (MPFS). You can locate this information by downloading the Physician Fee Schedule Relative Value File PFS Relative Value Files | CMS or by looking at the payment policy indicators in the Physician Fee Schedule search tool on the CMS website Search the Physician Fee Schedule | CMS.


These images from the Physician Fee Schedule Relative Value File and the Physician Fee Schedule search tool show the status indicator for several modifiers: multiple procedure (-51), bilateral surgery (-50), assistant surgeon (-80, -81, 82, -AS), co-surgeon (-62) and surgical team (-66) in relation to CPT code 33510 CABG single vein. The Assistant Surgeon status indicator for this code is “2” which means that assistant at surgery payment restrictions do not apply to this procedure. Since this is the case, when documentation supports the services of an assistant surgeon, the provider providing the assistance at surgery could report code 33510 with an applicable Assistant Surgeon modifier (-80, -81, -82, -AS) and could expect to be paid.

Physician Fee Schedule Relative Value Files

Physician Fee Schedule Relative Value Files

Physician Fee Schedule Search Tool

Physician Fee Schedule Search Tool

Regulation by circumstances

Sometimes whether or not assignment of a modifier is appropriate is determined by circumstances rather than by policy. Examples include:

Circumstances allow use of a modifier that is normally restricted

Payment may be made for the services of assistants at surgery in teaching hospitals notwithstanding the availability of a qualified resident to furnish the services if there are exceptional medical circumstances (e.g., emergency, life-threatening situations such a multiple traumatic injuries) which require immediate treatment. There may be other situations in which the medical staff may find that exceptional medical circumstances justify the services of a physician assistant at surgery even though a qualified resident is available. In these cases, the use of modifier -80 would be appropriate for use by the assistant surgeon.

Circumstances override the application of the status indicator

Except when documentation supports medical necessity, payment is not generally allowed for an assistant surgeon when payment for either two surgeons (modifier “-62”) or team surgeons (modifier “-66”) is appropriate. Therefore modifiers -80, -81, -82, -AS should not generally be appended to the same CPT code(s) where modifiers -62 or -66 are used even if the status indicator signals that use of these modifiers is allowed with that particular CPT code.

For details about how the use of Assistant Surgeon modifiers impacts provider reimbursement and for more examples of what circumstances qualify for reimbursement for assistance at surgery refer to chapter 12 of the Medicare Claims Processing Manual. Medicare Claims Processing Manual (

Take Aways

  • Physician or advanced practice clinicians who act as assistants at surgery must append a modifier to the CPT code(s) for the procedure to be reimbursed for their services.
  • Selecting the correct Assistant Surgeon modifier requires knowing the type of provider who assisted in the surgery and clear documentation of their level of involvement in assisting the primary provider.
  • That appropriateness of appending an Assistant Surgeon modifier to a particular CPT code is directed by status indicators. These indicators are found in the Medicare Physician Fee Schedule (MPFS).
  • For further details about the assignment of Assistant Surgeon modifiers, including the specifics of reimbursement, or for complex/exceptional cases, consult chapter 12 of the Medicare Claims Processing Manual for additional guidance. 

Need more information about appending modifiers related to the participation of more than one provider during a surgical procedure, such as co-surgeons or surgical team? Take the course below on


Since 1992, HIA has been the leading provider of compliance auditscoding support services and clinical documentation audit services for hospitalsambulatory surgery centersphysician groups and other healthcare entities. HIA offers PRN support as well as total outsource support.

The information contained in this coding advice is valid at the time of posting. Viewers are encouraged to research subsequent official guidance in the areas associated with the topic as they can change rapidly.

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