Incident To Billing Provision for California Workers' Comp

Contrary to popular belief, bills for services rendered by Physician Assistants or other NPPs may be reimbursed at 100% of the Official Medical Fee Schedule (OMFS). “Incident to” billing allows NPPs to bill with a physician’s National Provider Identifier (NPI) number – provided strict criteria concerning that physician’s supervision and availability are met.

Frequently Asked Questions

Q: What is “incident to” billing?

A: The “incident to” billing provision enables non-physician providers to bill with a physician’s National Provider Identifier (NPI) number for 100% of the OMFS. But there are strict criteria concerning the location of the service, physician proximity, and treatment timeline that must be met – we have the details below.

Q: Aren’t Physician Assistants and other non-physician providers billed at 85% of the OMFS?

A: In many cases, yes. But under certain circumstances, NPP services may be considered “incident to” those of a physician, and may then be billed using that physician’s NPI number for a 100% reimbursement. We break down the criteria below.


The CCR breaks down the incident to criteria by both setting and service type. While we strongly recommend reading and familiarizing yourself with the official regulations, we’ve summarized the key points and terms below.

Non-Institutional Setting

Non-Institutional Setting refers to services rendered in any setting that isn’t a hospital or a skilled nursing facility. When NPPs render certain services under direct supervision, these services may be considered “incident to” the supervising physician and may be billed using that physician’s NPI for a 100% reimbursement.

Services occurring in an institutional setting – that is to say a hospital or skilled nursing facility – are not eligible for incident to billing.

Incident to Professional Services

Per the CCR, the incident to provision refers to a physician’s professional services that “are furnished as an integral, although incidental, part of the physician’s personal professional services in the course of diagnosis or treatment of an injury or illness.”[1] In other words, this covers routine services that occur in a physician’s office.

Furthermore, any charges for these services must typically be included in the physician’s bill.[2] Any service that typically takes place outside of the office setting – surgical procedures, for example – are not covered under incident to billing.

It's important to note that only physicians may initiate patient care, conduct initial evaluation and management, and establish an ongoing treatment plan. This means that incident to services may not be provided on an injured worker's first treatment or any time their ongoing treatment plan changes.

Direct Personal Supervision Criteria

When a physician supervises NPP to assist with services, the physician may include the charges for the NPP on the physician’s bill and be reimbursed 100% of the OMFS for the NPP’s services.  In order to be considered, and subsequently reimbursed as services incident to those of a physician, the NPP incident to service must always:

  • Be performed under direct supervision by the physician.
  • In office settings, the physician isn’t required to be present in the same room – but they must be in the same office suite, and available to provide immediate assistance or direction.
  • Outside office settings, NPP services are only incident to those of a physician if there is direct supervision.
  • If the physician is in the same institution, but not the same office suite, the services are not eligible for incident to billing – even if the physician is available by telephone.

If the above criteria are not met, services rendered by NPPs are billed under the NPI number of the NPP and reimbursement is 85% of the OMFS.


An orthopedist examines an injured worker and schedules a follow-up visit. At the follow-up visit, a physician assistant examines the patient and prescribes medication. If the orthopedist is available on-site, in the same suite and able to step in if needed, the physician assistant’s services are considered incident-to and payable at 100% of the OMFS.

Additional Information

DWC: Physician Fee Schedule Regulations 

DaisyBill Resources

Blog Post: Incident To Billing for CA Workers’ Comp

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[1] See page 24 of the DWC’s Physician Fee Schedule Regulations for more information.

[2] Again, page 24 of the DWC’s Physician Fee Schedule Regulations has the details.

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