👩⚕️ Modifier -FS: Split or Shared Evaluation and Management Visit
Quick reference
- Definition: Modifier -FS identifies an E/M visit furnished jointly by a physician and a nonphysician practitioner (NPP) from the same group in a facility setting, where either clinician could have billed the visit independently.¹
- Pairs with: No required pairing modifier; -FS stands alone on the E/M code, though critical care claims may also require time documentation to support the reported code level.²
- Key rule: Payment goes to whichever practitioner performed the “substantive portion” of the visit — defined as more than half of the total combined time, or a substantive part of the medical decision making (MDM) — and -FS must be appended regardless of which practitioner ends up billing.³
When to use -FS
Use -FS when:
- Do append -FS: A physician and an NPP (nurse practitioner, physician assistant, or clinical nurse specialist) from the same group practice each personally perform part of the same E/M encounter for the same patient on the same calendar date.⁴
- Do append -FS: The encounter occurs in a recognized facility setting — hospital inpatient, hospital outpatient, observation, emergency department, or skilled nursing facility — where incident-to billing rules do not apply.⁵
- Do append -FS: The billing practitioner (whichever one performed the substantive portion) is reporting an E/M code such as 99223, 99233, or 99291 that qualifies for split/shared billing under CMS rules.²
When NOT to use -FS (common denials)
Do NOT use -FS when:
- Don’t append -FS to E/M visits performed in a non-facility, office-based setting — CMS explicitly prohibits -FS outside of hospital inpatient, hospital outpatient, observation, ED, and SNF settings, since office encounters fall under incident-to rules instead.⁶
- Don’t append -FS when only one practitioner (physician or NPP alone) provided the entire visit without any distinct, personally performed contribution from a second clinician in the same group.¹
- Don’t append -FS to non-E/M procedure codes or diagnostic tests; the modifier is restricted to E/M service lines only, not to procedures performed during the same encounter.⁴
Substantive Portion Determination Rule
This is the governing CMS policy that determines which practitioner bills the split/shared visit and therefore which NPI the -FS-modified claim is submitted under.
CMS finalized this definition effective January 1, 2024, and it remains unchanged through 2026.³
- Time-based substantive portion: The billing practitioner personally spent more than half of the total combined time both clinicians spent on the visit; overlapping time where both clinicians are jointly present (e.g., meeting with the patient together) counts only once, not twice.⁷
- MDM-based substantive portion: The billing practitioner personally made or approved the management plan and assumed responsibility for it, including the associated risk of complications, morbidity, or mortality — this applies to most E/M levels but is calculated differently for critical care.³
- Critical care exception: For 99291 and 99292, the substantive portion is determined by time only (not MDM), and the billing practitioner must personally furnish more than half of the total critical care time; if the physician’s time alone doesn’t reach the threshold for 99292 add-on reporting, cumulative time from both clinicians combined can still support the base code.⁸
What you’re paid for with -FS (reimbursement concept)
Split/shared visits are paid at the standard Medicare Physician Fee Schedule (MPFS) rate for the reporting practitioner’s NPI — full physician-fee-schedule rate if billed under the physician, or 85% of the physician fee schedule if billed under the NPP, consistent with standard NPP payment differentials.⁹ The -FS modifier itself carries no separate payment or RVU adjustment; it is a tracking and attribution modifier that tells Medicare the visit was jointly performed, not a payment-multiplier modifier like -50 or -52.⁴
Documentation checklist (what has to exist)
To support -FS, the record should show:
- A discrete, signed and dated note entry (or clearly attributed portion of a shared note) from each participating clinician reflecting their own personally performed work, not a single unattributed combined note.¹⁰
- Explicit time documentation for both clinicians if time is used to determine the substantive portion, or a clear statement of who made/approved the medical decision making and assumed responsibility for it if MDM is used instead.³
- No indication that the encounter occurred in a non-facility office setting, since -FS claims submitted for office visits are subject to automatic denial under current MAC edits.⁶
Common uses (Hospital/Facility context)
Split/shared billing with modifier -FS appears most often on hospitalist and hospital-based specialty services where a physician and an NPP round together, such as initial hospital care, subsequent hospital care, and hospital discharge management. In critical care units, -FS is commonly applied when a physician and an NPP jointly manage a critically ill patient and their combined time meets the threshold for 99291 (first 30-74 minutes) with 99292 reported for each additional 30 minutes beyond that. In emergency department and observation settings, -FS is used when an NPP performs the initial workup and a supervising physician completes and documents a substantive review of the MDM before the encounter closes.
This modifier does not apply to office-based ophthalmology, urology, or ENT visits billed under incident-to rules, since those follow a separate supervision-based framework rather than the split/shared model.
Quick self-check before using -FS
- Did this visit occur in a genuine facility setting (hospital inpatient, hospital outpatient, observation, ED, or SNF) rather than an office or clinic?
- Did both the physician and the NPP personally document distinct, non-overlapping time or MDM contributions to this specific encounter?
- Can the practice clearly identify which practitioner met the substantive-portion threshold (more than half of total time, or the MDM-based portion), and is that the practitioner the claim is being billed under?
- For critical care services, was the substantive portion determined strictly by time rather than MDM, consistent with the critical care exception?
📎 Sources
1. Centers for Medicare & Medicaid Services. *Split (or Shared) Evaluation and Management Visits — Medicare Claims Processing Manual Updates.* CMS; 2024-2026. 2. American College of Emergency Physicians. *Shared Services FAQ.* ACEP; 2024-2025. 3. American Academy of Family Physicians. *E/M Coding: Guidelines and FAQs — Split or Shared Visits.* AAFP; 2024. 4. Noridian Healthcare Solutions. *Modifier FS — JE Part B.* Noridian Medicare; 2025. 5. CodingIntel. *CMS's 2024 Shared or Split Services Policy (Unchanged 2025-2026).* CodingIntel; 2024.Sources listed above correspond to superscript citations throughout this note. Verify all Medicare payment figures against your current CMS PFS Lookup tool and applicable MAC LCD prior to claim submission. Please use the latest AAPC/AHIMA Coding Books to verify each code within this note.