Incident to billing is the Medicare rule that lets a service furnished by your staff be billed under the supervising physician’s National Provider Identifier, at 100 percent of the Physician Fee Schedule amount, instead of under a nurse practitioner’s or physician assistant’s own NPI at 85 percent. The conditions live in 42 CFR 410.26. The service has to be furnished in a noninstitutional setting, it has to be an integral though incidental part of the physician’s own service, the physician has to have personally performed an initial service and stay actively involved in the course of treatment, and the staff member has to work under direct supervision.
Incident to billing is the office rule. In a hospital or skilled nursing facility, the same physician and nonphysician practitioner pairing follows a different one, the split/shared visit billing rules, where the provider who performs the substantive portion bills the visit.
There is one thing about incident to billing that trips up almost every practice adding an ancillary service, and it is worth stating up front: diagnostic tests are not incident to services. They sit in their own Medicare benefit category, and they follow a separate supervision rule at 42 CFR 410.32. If you are adding in-office vascular or autonomic testing, the incident to billing checklist is not the checklist you need. This guide covers both, plus the supervision change that took effect January 1, 2026.
What is incident to billing?
Incident to billing is a coverage provision, not a code. It says that services and supplies furnished by auxiliary personnel can be covered under Part B as though the physician furnished them, so long as a specific set of conditions is met. The practical effect is a payment difference. A service billed under the physician’s NPI is paid at the full fee schedule amount. The same service billed under a physician assistant’s NPI is capped at 85 percent of the physician fee schedule amount under 42 CFR 414.52(d), and a nurse practitioner’s or clinical nurse specialist’s services are capped at the same 85 percent under 42 CFR 414.56(c).
That 15 point spread is why incident to billing gets so much attention in independent practices. It is also why it gets audited. The conditions are not paperwork formalities, and a practice that treats them that way is exposed on every claim it submits.
What are the requirements for incident to billing?
Seven conditions have to hold at once. Six come straight from 42 CFR 410.26 and the Medicare Benefit Policy Manual; the seventh is the one auditors actually ask about.
- Noninstitutional setting. The service must be furnished in a noninstitutional setting to a noninstitutional patient. Incident to billing does not apply in a hospital or a skilled nursing facility.
- Integral though incidental. The service must be an integral, though incidental, part of the physician’s service in the course of diagnosis or treatment. It cannot be a freestanding service the patient came in for on its own.
- Commonly furnished in an office. The service must be the kind commonly furnished in a physician’s office or clinic, and commonly furnished without a separate charge.
- Direct supervision. The physician or other qualified practitioner must supervise directly. Certain care management and behavioral health services are the narrow exceptions that may be furnished under general supervision.
- A physician-initiated course of treatment. The physician must have personally performed an initial service and must remain actively involved in the course of treatment. A brand new problem on a follow-up visit is not covered by the earlier encounter.
- Scope of practice and state law. The staff member must be permitted to furnish the service under state law and under the terms of their license or certification.
- An employment relationship. The person furnishing the service must be auxiliary personnel of the physician or of the entity that employs or contracts with the physician.
Requirement five is where most incident to billing denials originate. The physician’s initiating service establishes the plan of care, and everything billed incident to it has to fall inside that plan. When a patient raises something new, the visit belongs to whoever evaluates it.
Who counts as auxiliary personnel?
Broadly, anyone acting under the physician’s supervision who meets state licensure requirements and has not been excluded from federal health care programs. CMS defines auxiliary personnel to include an employee, a leased employee, or an independent contractor of the physician or of the legal entity that employs or contracts with the physician. Nurse practitioners, physician assistants, registered nurses, licensed practical nurses and medical assistants can all be auxiliary personnel for incident to billing purposes, provided the specific service is inside their state scope of practice.
Note what that definition does not require. It does not require that the person be a W-2 employee. And in a group practice or an organized clinic, CMS has long held that supervision can be shared among several physicians, so the physician who ordered a service need not be the one supervising it that day. That flexibility is set out in the Medicare Benefit Policy Manual at Chapter 15, section 60.3, and it is what makes incident to billing workable in a multi-provider office.
What changed for incident to billing in 2026?
The definition of direct supervision changed permanently. In the CY 2026 Physician Fee Schedule final rule issued October 31, 2025, CMS finalized a definition of direct supervision that lets the supervising practitioner be immediately available through real time audio and visual interactive telecommunications rather than physically present in the office suite. Audio-only does not qualify.
Two details matter for planning. First, CMS applied this to incident to services under 410.26 and to diagnostic tests under 410.32, along with pulmonary rehabilitation under 410.47 and cardiac and intensive cardiac rehabilitation under 410.49. Second, services with a global surgery indicator of 010 or 090 are carved out, so virtual direct supervision does not reach those. Everything took effect January 1, 2026.
Before 2026 this flexibility was a temporary extension that practices had to re-check every year. It is now the standing definition, which makes single-physician and multi-site groups meaningfully easier to staff. It is a rule about where the supervising practitioner can be. It does not turn an in-office test into a remote service, and it does not change who may operate the equipment.
The same rule set the CY 2026 conversion factors. Beginning this year there are two: $33.57 for qualifying alternative payment model participants and $33.40 for everyone else, both up from $32.35.
Does incident to billing apply to diagnostic tests?
No. This is the single most consequential misunderstanding in the area, and it has a clean regulatory basis. 42 CFR 410.26 excludes from incident to coverage any service that has its own Medicare benefit category. Diagnostic tests have one: they are covered under section 1861(s)(3) of the Social Security Act, and their conditions of coverage sit at 42 CFR 410.32. So a diagnostic test is never billed “incident to” a physician’s service. It is billed as a diagnostic test, under the supervision level that CMS assigns to it.
Practices know they need an answer about delegation. They just look for it under the wrong rule, because incident to billing is the phrase everyone learns first.
Two rules diverge in ways that matter operationally:
| Question | Incident to services (410.26) | Diagnostic tests (410.32) |
|---|---|---|
| Minimum supervision | Direct supervision, with narrow general-supervision exceptions | At least general supervision; some tests require direct or personal |
| Order required? | Part of the physician’s existing plan of care | Must be ordered by the physician treating the beneficiary |
| Setting | Noninstitutional only | Not limited the same way |
| Who may furnish | Auxiliary personnel under supervision | Physician, or NP, CNS, PA, CRNA or CNM within state scope of practice |
| Where the level is published | Not code-specific | Assigned per code in the CMS Physician Fee Schedule relative value files |
What supervision level does an in-office diagnostic test require?
At minimum, general supervision. CMS defines the three levels precisely in 410.32(b)(3), and the differences are physical:
- General supervision: the procedure is furnished under the physician’s overall direction and control, but the physician’s presence is not required while it is performed.
- Direct supervision: the physician must be present in the office suite and immediately available to furnish assistance and direction throughout the procedure. Presence in the room is not required, and as of January 1, 2026 immediate availability can be satisfied by real time audio and video.
- Personal supervision: the physician must be in attendance in the room while the procedure is performed.
Every diagnostic test payable under the fee schedule requires at least general supervision, and some require more. The level is not a judgment call. It is published per code in the CMS Physician Fee Schedule relative value files, in the physician supervision of diagnostic procedures indicator, and your Medicare Administrative Contractor publishes the same values in its fee schedule lookup. Check the code you intend to bill rather than assuming the level, and re-check it when the annual file updates. For the ABI-specific version of this question, including CPT 93923, see our guide to who can perform an ABI test and our ABI CPT code 93923 billing guide.
How does this affect a practice adding in-office testing?
It changes which questions you have to answer before the first patient is scheduled. A practice that plans its staffing around incident to billing will build the wrong workflow for a diagnostic service, because it will design for direct supervision and a physician-initiated plan of care when the governing rule may only require general supervision and a written order. The reverse error is just as costly: applying diagnostic-test logic to a service that really is subject to incident to billing leaves the supervision requirement unmet.
Non-invasive physiologic studies are a good illustration. The CMAT Advantage system that HealthWright Technologies places in independent practices is non-invasive and built on FDA-cleared component devices, with clearance held by LD Technology, and a full study takes 7 to 10 minutes. It captures ankle-brachial index, toe-brachial index, volume plethysmography, heart rate variability, Ewing tests, sudomotor function and galvanic skin response in a single sitting.
Nothing in that list is a specimen-based laboratory test, and nothing in it is an evaluation and management service. Each measurement is a diagnostic test. That is why our read is that the incident to billing framework at 410.26 is the wrong lens for this kind of platform, and 410.32 is the right one. Confirm the supervision indicator for your specific codes before you finalize a staffing plan.
The practical build looks like this. Decide which clinician signs the order. Confirm the supervision level for each code. Verify that the staff member who will run the test is permitted to do so under your state’s scope of practice rules. Document competency for that person, and keep the documentation current. Then decide, separately, which of your evaluation and management and care management services genuinely qualify for incident to billing, because those are the services the 410.26 conditions were written for.
Practices weighing whether a new diagnostic service is worth the operational lift will find the financial side covered in our overview of ancillary revenue for medical practices. If your interest is preventive and quality-program driven, our piece on diagnostic testing for value-based care takes that angle, and the annual wellness visit CPT code guide covers the preventive visit those tests often sit alongside.
What are the most common incident to billing mistakes?
Four incident to billing errors recur often enough to be worth a standing internal check.
- Billing a new problem incident to an old plan. If the patient presents with a condition the physician has not evaluated, the encounter is not incident to anything.
- Assuming incident to billing works in the hospital. It does not. The setting condition is absolute.
- Applying the incident to checklist to a diagnostic test. Wrong rule, and it produces both over-staffing and unsupported claims.
- Treating supervision as a policy document rather than a daily fact. Supervision has to be real on the date of service, and it has to be provable.
Commercial payers add a fifth complication. Incident to billing is a Medicare construct, and commercial plans are free to write their own credentialing and supervision terms. Read the contract rather than assuming Medicare rules carry over.
Frequently asked questions about incident to billing
Can a medical assistant’s work be billed incident to a physician’s service?
Yes, if the specific task is within what state law and the medical assistant’s certification permit, and if all of the other incident to billing conditions are met. State scope of practice rules vary considerably, so the answer is set by your state rather than by CMS.
Does the supervising physician have to be in the room?
No. Direct supervision means present in the office suite and immediately available to give assistance and direction, not in the room. Only personal supervision requires attendance in the room, and that level applies to a small subset of diagnostic tests.
Can direct supervision be provided by video in 2026?
Yes. CMS permanently adopted a definition of direct supervision that allows immediate availability through real time audio and visual interactive telecommunications, effective January 1, 2026. Audio-only does not satisfy it, and services with a global surgery indicator of 010 or 090 are excluded.
Why is a diagnostic test not billed incident to a physician’s service?
Because it has its own Medicare benefit category under section 1861(s)(3) of the Act, and 42 CFR 410.26 excludes services with their own benefit category from incident to coverage. Diagnostic tests are governed by 42 CFR 410.32, which requires a physician order and assigns a supervision level per code.
What is the payment difference between incident to billing and billing under an NPP’s own NPI?
A service billed incident to a physician’s service is paid at the full Physician Fee Schedule amount under the physician’s NPI. A service billed under a physician assistant’s, nurse practitioner’s or clinical nurse specialist’s own NPI is capped at 85 percent of the physician fee schedule amount under 42 CFR 414.52 and 414.56.
Talk through the staffing model before you buy the equipment
HealthWright Technologies has supplied diagnostic and therapeutic devices to independent physicians since 2000, and every placement includes training, implementation support and billing guidance for the practice team. If you are mapping out who will run a test and how it will be documented, that conversation is worth having before the purchase rather than after. Reach us at healthwrighttechnologies.com/contact or contact@healthwrighttechnologies.com. Our office is at 60 Bear Creek Marina Road, Mansfield, GA 30055, and the main line is (678) 322-7146.
Primary sources for this article: 42 CFR 410.32 and the CMS CY 2026 Physician Fee Schedule final rule fact sheet.
This article is general information about Medicare billing policy, not legal, coding, or medical advice. Verify all supervision levels and coverage conditions with your Medicare Administrative Contractor, your payer contracts, your state scope of practice rules, and your own compliance counsel before changing a billing or staffing practice. Consult your healthcare provider before starting any new treatment. CPT is a registered trademark of the American Medical Association. All CPT code descriptions, coding rules, and payment policies are subject to change; confirm current requirements with CMS, your MAC, and the AMA CPT codebook.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis, treatment, and clinical decision-making.
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