Reassignment, NPP Supervision & Compliance
Solo practices have it simpler, one NPI, one provider, one set of billing rules. The moment you add a second provider, a mid-level, or a group entity, the billing picture gets more complicated. Reassignment agreements, supervision requirements, group vs. individual NPIs, and locum arrangements all introduce compliance exposure that most multi-provider practices don't fully understand until a payer audit finds the gaps. The financial stakes here are real: a recurring gap in this area adds up to lost or delayed revenue every month.
Here's a practical breakdown of what group practice billing actually requires in 2026.
If your group is managing these billing rules without a specialist, our specialty clinic billing services can help you stay compliant and stop leaving money on the table.
When a provider employed by or contracted with a group practice wants their Medicare payments to go to the group (not to them personally), they need to file a reassignment of benefits. This is done via CMS Form 855R or as part of the group enrollment process.
Without a valid reassignment on file, a provider can't bill under the group's NPI for Medicare purposes. Claims will either deny or, if they accidentally pay, become subject to take-backs when audited. This is one of those things that gets set up once and forgotten, then causes a massive problem when a new provider joins and someone assumes the paperwork handled itself.
Both. For most professional claims (CMS-1500), Box 24J contains the rendering provider's individual NPI, and Box 33a contains the billing/group NPI. The rendering provider is who actually performed the service. The billing provider is the group entity that receives payment.
Getting this wrong is more common than you'd think. Groups that accidentally bill with only the group NPI in both fields create records that can't be traced to a specific provider, which causes problems during audits and credentialing verification. Groups that use only the individual NPI miss the reassignment entirely.
How you supervise, and document supervising, nurse practitioners, physician assistants, and other NPPs determines whether you bill at 100% or 85% of the Medicare fee schedule, and whether the service qualifies as incident-to.
| Level | What It Means | When It Applies |
|---|---|---|
| General | Physician available by phone; doesn't need to be on-site | Most diagnostic tests ordered by NPPs |
| Direct | Physician physically present in the office suite (not necessarily same room) | Incident-to services, certain procedures |
| Personal | Physician in the room, immediately available to assist | High-risk procedures, certain diagnostic studies |
Incident-to billing, billing NPP services under the physician's NPI at 100%, requires direct supervision. The physician must be physically present in the office suite when the NPP sees the patient. Not available by phone. Not in a different building. In the suite.
If the physician isn't present and you bill incident-to anyway, that's a false claim. It's one of the most common compliance violations in multi-provider practices, not because practices are trying to commit fraud, but because the front desk checks the supervising physician's schedule without realizing they left early.
When both a physician and an NPP perform substantive portions of an E/M visit, it's a split/shared visit. CMS rules effective 2024 require that the physician perform the "substantive portion", defined as more than half the total time, or completing the history, physical exam, or medical decision making, in order to bill under the physician's NPI.
Documenting split/shared correctly means both providers document their contributions separately, and the billing provider is clearly identified as the one who performed the substantive portion. A note that just says "I reviewed and agree with Dr. Smith's note" doesn't establish a split/shared visit; it establishes a co-signature, which is different.
When your regular physician is out and you bring in a locum to cover, you can bill under the regular physician's NPI using modifier Q6, as long as the arrangement is a temporary fill-in (not a permanent hire disguised as locum) and you're paying the locum on a per-diem or per-visit basis, not through the practice's standard payroll.
The Q6 modifier tells Medicare "a substitute physician was used." It's only valid for 60 continuous days. If a locum stays longer, they need to enroll as a provider under your group, not stay as locum indefinitely.
Whether a provider is an employee or an independent contractor doesn't change the billing mechanics much; both can have reassignment on file and bill under the group NPI. Where it matters is compliance: independent contractors create risk if they're functionally operating like employees (using your equipment, following your schedules, seeing only your patients). The IRS has a specific test for worker classification, and misclassification in healthcare carries both employment tax exposure and Stark Law implications.
If your group practice offers group therapy sessions (mental health, SUD, or chronic disease management), the billing rules are different from individual visits. Group psychotherapy bills under 90853. Each patient in the session gets their own claim, the same code, the same date of service, the same provider. The session note should document that a group session occurred, the therapeutic content, and each patient's participation and response.
Some payers limit group therapy to specific session sizes (typically 8–12 patients). Exceeding those limits without documentation of clinical rationale can result in retroactive denials.
In a group, billing errors often come from an out-of-date provider list. Keep a roster with each provider's NPI, taxonomy, license, payer enrollment dates, and reassignment status, and have one person own it. When a provider joins, leaves, or changes locations, the roster is updated the same day and the billing system follows.
Review it monthly against the schedule. If someone is seeing patients for a payer they aren't enrolled with, you want to find out before the claims go out.
Both. On a CMS-1500, Box 24J carries the rendering provider's individual NPI and Box 33a carries the billing group's NPI. The rendering provider is the person who actually performed the service.
The article says you can bill under the regular physician's NPI with modifier Q6, as long as the arrangement is a temporary fill-in and not a permanent hire disguised as a locum. Keep the dates and coverage arrangement on file.
Group psychotherapy bills under 90853, and each patient in the session gets their own claim. The rules differ from individual visits, so the record should show each patient's participation.
The billing gaps most practices don't catch until they show up as denials. Get the checklist: free, no spam.
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Revenue check: Contractors can look back three years, and on a practice with a recurring pattern here, that lookback can put a large recoupment at stake, before the cost of the appeal. Run a quarterly sample of 20 to 30 claims in this category against the supporting documentation. It's a small time investment that reliably catches five-figure problems before a payer does.
Keep this on a schedule: Run a quarterly sample of 15 to 20 claims in this category against the chart. It typically costs an hour of staff time and catches problems in the $8,000 to $20,000 range long before a payer review does.
We audit group practice billing structures (NPP supervision, reassignment gaps, split/shared documentation), and fix the compliance issues before a payer does.
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