In hospital settings, a physician and an NP or PA often each see the same patient on the same day. The visit is billed once, and the main question is who bills it. Medicare answers that with a rule called the substantive portion, and getting it wrong can mean a denial, a payment at the wrong rate, or an audit finding.
This post covers where split (or shared) billing applies, how to decide who bills, what to document, and how to report the visit on the claim.
What Is a Split (or Shared) E/M Billing Visit?
CMS defines a split (or shared) visit as an evaluation and management (E/M) visit in which a physician and a nonphysician practitioner (NPP), such as a nurse practitioner or physician assistant, each perform part of the visit. Both must be in the same group, and the visit is billed under the practitioner who performed the substantive portion.
The policy applies only in facility settings, such as hospital inpatient and outpatient departments and emergency departments, and CMS also applies it in other institutional settings like skilled nursing facilities. It does not apply in the office. Office visits shared with an NPP fall under incident-to rules, which have different supervision and billing conditions. Check the place of service before you apply split/shared rules, since using the wrong policy is one of the most frequent errors.
Basic Requirements
For Medicare, a split (or shared) visit generally needs all of the following:
- The service is an E/M visit that CMS allows to be billed as split/shared, in a facility setting.
- A physician and an NPP in the same group each furnish part of the visit, on the same calendar date.
- The practitioner who performed the substantive portion bills the visit.
- The medical record documents the work of both and identifies who did what.
- The claim carries modifier FS.
Confirm the details, including which services qualify, in the Medicare Claims Processing Manual and your MAC’s guidance.
How to Decide Who Bills: The Substantive Portion
Under the current CMS definition, the substantive portion is either more than half of the total time spent by the two practitioners, or a substantive part of the medical decision making (MDM). Use whichever method fits the encounter, and document it. Critical care visits are measured by time only.
By time. Add together the time each practitioner spent on the patient on that date. Whoever spent more than half bills the visit. If both were in the room together, that overlapping time counts once toward the total. Here is an example with made-up numbers: the NP spends 20 minutes and the physician spends 12 minutes separately. The total is 32 minutes, and the NP spent more than half, so the NP bills.
Only countable activities add to the total. These include reviewing records, taking history, examining the patient, counseling, ordering tests, documenting, and care coordination that is not billed separately. Travel time, separately reported services, and teaching that is not specific to the patient do not count.
By MDM. The billing practitioner must have made or approved the management plan and taken responsibility for it. A signature on the note without involvement in the decisions is not enough.
For the 2024 and 2025 rules, CMS also allowed history or exam as a basis, but for 2026 the definition follows the CPT guidelines, which use time or MDM. Sources describe the transition slightly differently, so confirm the current wording in the CY2026 Physician Fee Schedule final rule and 42 CFR 415.140.
Documentation Requirements
The record needs to show what happened in a way that an auditor can follow. At a minimum:
- Both practitioners are identified, with credentials and their roles in the visit
- The documentation supports the E/M level billed, combining the work of both
- It shows which practitioner performed the substantive portion and whether time or MDM was used
- If time was used, total time and who spent how much are recorded
- The billing practitioner reviews, signs, and dates the record
Templates help, but copied text that does not match the actual encounter creates risk. A plain attestation that states what each practitioner did and which method was used is usually clearer than a generic statement.
Reporting the Visit and Payment
Append modifier FS to the E/M code on the claim. It tells Medicare that the visit was split or shared. Do not use modifier 52 for this purpose, since it reports a reduced service. Bill under the NPI of the practitioner who performed the substantive portion.
Payment follows the billing practitioner. If the physician bills, Medicare pays at 100 percent of the fee schedule amount. If the NPP bills, it pays 85 percent. This is why a mismatch between the billing NPI and the documentation matters, since it changes the payment and can draw a post-payment review. Our post on claim scrubbing techniques explains how to set up edits that flag a missing FS modifier before the claim goes out.
Commercial payers do not all follow Medicare’s rules. Some recognize modifier FS and pay as CMS does, while others require different modifiers, apply their own payment rules, or do not allow shared billing at all. Check each payer’s policy and avoid assuming Medicare rules apply.
Common Split/Shared Billing Errors
- Applying split/shared rules in the office instead of incident-to
- Leaving off modifier FS
- Billing under the physician when the NPP performed the substantive portion
- Counting overlapping time twice
- Relying on a cosignature alone to show the physician’s involvement
- Documentation that does not identify both practitioners
- Mixing methods, for example documenting time but billing by MDM without support
When to Get Outside Help
These errors usually appear later as underpayments or denials, and they take time to trace back to documentation. Rapid RCM Solutions provides AR and denial management for practices that need claims reviewed, denials worked, and billing patterns checked for issues like missing modifiers and mismatched billing NPIs.
Conclusion
For Medicare, a split or shared visit is billed under the practitioner who performed the substantive portion, based on time or MDM. It needs a facility setting, documentation of both practitioners, and modifier FS on the claim. Check that your documentation supports who billed, and review commercial payer rules separately.
Frequently Asked Questions
What is modifier FS?
Modifier FS is the HCPCS modifier that identifies a split (or shared) E/M visit on a Medicare claim. It is required when the visit is billed this way.
Can split/shared billing be used in an office?
Not under Medicare. It applies in facility settings. In the office, an NPP’s services are billed under incident-to rules or under the NPP’s own NPI.
How much does Medicare pay for a split/shared visit?
It depends on who bills. A physician billing receives 100 percent of the fee schedule amount, and an NPP billing receives 85 percent.
Do commercial payers follow Medicare’s split/shared rules?
Some do, but many have their own policies. Check each payer’s provider manual before billing.
