Split/Shared Visit Rules: Who Bills and How to Prove It

For facility E/M encounters, Medicare pays the clinician who performed the substantive portion of the visit, defined as more than half the total combined time or the substantive part of medical decision making (MDM). That's the standard set by 42 CFR § 415.140, and it hasn't changed since the transitional time-only rule expired at the end of 2023. If you bill Medicare for physician and non-physician practitioner (NPP) teams working the same facility encounter, three actions protect the claim right now:

• Determine the substantive portion using total time (more than 50%) or MDM, then bill under the NPI of whichever clinician met that threshold.
• Append modifier FS to the E/M code every time a split/shared visit is reported, per CMS guidance.
• Get the billing clinician's signature and date on the note, along with documentation identifying both practitioners and specifying who did the substantive work.

Miss any one of these three, and you've handed an auditor a denial on a silver platter. The rest of this guide walks through the mechanics, the documentation standards, and the scenarios where billing teams most often get it wrong.

Key Takeaways

Split/shared visit billing succeeds when the substantive-portion determination, whether time or MDM, is documented with specific, itemized evidence and matched to the correct billing NPI and modifier.

Table of Contents

• Split Shared Visit Rules: Definition and Scope Under Medicare
• How to Determine the Substantive Portion: Time vs. MDM
• Settings and Exclusions: Where Split Shared Billing Applies
• Documentation Requirements: Signatures and Provable Substantive Work
• Claim Submission Mechanics: Modifier FS and Billing Provider NPI
• Critical Care and Prolonged Services Under Split Shared Rules
• Worked Examples for Time and MDM Determinations
• Compliance and Audit Mitigation Using HIMShield Insights
• What Actually Matters Here
• Sources

Split Shared Visit Rules: Definition and Scope Under Medicare

A split (or shared) visit is a single evaluation and management encounter performed jointly by a physician and an NPP, such as a nurse practitioner or physician assistant, who belong to the same group. CMS finalized the current substantive-portion standard in the CY 2024 Physician Fee Schedule final rule, and 42 CFR § 415.140 supplies the legal definition billing teams rely on today.

The rule applies only in facility settings. That distinction trips up more billing departments than any other part of this policy.

• Eligible settings: hospital inpatient, hospital outpatient departments, the emergency department, observation, and skilled nursing facilities (SNF) when the visit is billed under Part B facility rules.
• Excluded setting: office visits (place of service 11) never qualify for split/shared billing, regardless of how the work was divided between physician and NPP.
• Qualifying service: the E/M service reported must be one that either the physician or the NPP could have billed independently under Medicare's own scope-of-practice rules for that credential.

Group membership matters here too. Both practitioners have to bill under the same group for the visit to qualify as split/shared, which ties directly into how your practice defines participating provider relationships in your credentialing files. Get the setting or the group relationship wrong, and the entire claim rests on a definition that doesn't apply.

How to Determine the Substantive Portion: Time vs. MDM

The 2024 revision replaced the old "personally performed" standard with a cleaner test: whoever performed more than half of the total time or the substantive part of the MDM bills the visit. You choose one method per encounter, not both, and the choice depends on what your documentation actually supports.

Here's the process for a time-based determination:

1. Log each clinician's time separately. Include face-to-face time and qualifying non-face-to-face work performed on the date of the encounter, such as chart review or care coordination.
2. Sum both times to get the total time attributed to the visit.
3. Calculate each clinician's share. Whoever contributed more than 50% of the combined total is the billing practitioner.
4. Document the source of each time entry. A vague "20 minutes" note with no activity description won't survive an audit request.

MDM-based determination works differently. Instead of a percentage, you're identifying which clinician performed the substantive part of the decision-making, meaning the assessment, the differential, the risk and benefit discussion, and the final plan. A note that simply restates findings without showing whose clinical reasoning drove the plan doesn't meet the bar. The chart needs to show, in the billing clinician's own documented reasoning, that they owned the decision-making that determined the visit's level.

Pro Tip: Build separate time fields into your EHR templates for physician time and NPP time, rather than one shared free-text box. It makes the more-than-half calculation auditable in seconds instead of a manual chart review during an appeal.

Two service types stay on the time-only standard regardless of the 2024 change: critical care and certain prolonged services. Both are covered in more detail further down, but if you're billing either one under split/shared rules, MDM never enters the equation.

Settings and Exclusions: Where Split Shared Billing Applies

CMS built this framework around facility-based care, and the setting list is narrower than many billing teams assume.

• Hospital inpatient: the most common application, particularly on medicine and surgical services where hospitalist and APP teams round together.
• Emergency department: high-volume ED groups frequently pair physicians and NPPs on the same patient, making accurate time and MDM documentation essential.
• Hospital outpatient departments and observation: both qualify, provided the group relationship and facility place-of-service code are correctly reported.
• Skilled nursing facilities: SNF visits billed under Part B facility rules qualify; long-term care (LTC) billing under different payment structures may not, so verify the specific benefit category before applying split/shared logic.

Office visits are explicitly excluded, full stop. If your practice bills primarily in an outpatient clinic setting with the occasional hospital consult, don't assume the same joint-documentation approach carries over. Getting the place of service code wrong on a claim is often the first domino that leads to a split/shared denial.

One more wrinkle: individual hospitals can, and often do, impose documentation standards stricter than what CMS requires, including a hospital-specific requirement that the physician have direct face-to-face contact even in scenarios where CMS would otherwise allow MDM-based billing. Check facility policy before assuming Medicare's floor is your ceiling.

Documentation Requirements: Signatures and Provable Substantive Work

Auditors don't take your word for who did the substantive portion. They want to see it in the chart, in specific, non-generic language, tied to a signature and a date.

• Identify both practitioners by name and role in the note, even when only one of them bills.
• State explicitly who performed the substantive portion, whether that's a time statement ("Dr. Alvarez performed 22 of 35 total minutes") or an MDM statement describing the billing clinician's own reasoning.
• The billing practitioner must sign and date the record, per the documentation standard in 42 CFR § 415.140.
• Separate face-to-face and non-face-to-face time entries so combined totals hold up if a payer requests a breakdown.
• Avoid templated or identical attestation language across multiple encounters. Auditors flag boilerplate phrases like "reviewed and agree with plan" appearing verbatim across dozens of charts, since it suggests the substantive work wasn't independently documented.

Pro Tip: If your NPP and supervising physician tend to use the same three attestation sentences on every chart, that pattern alone is enough to trigger a targeted payer audit. Vary the language to reflect the actual clinical reasoning each time.

For teams building out chart templates, reviewing concrete documentation examples side by side with actual denial letters is one of the fastest ways to see the gap between what your EHR captures and what an auditor expects.

Claim Submission Mechanics: Modifier FS and Billing Provider NPI

Once you've identified the billing practitioner, the claim itself has to reflect that determination cleanly.

1. Append modifier FS to the E/M CPT code on every split/shared claim, as outlined in the CMS E/M Services Guide.
2. Submit the claim under the NPI of the practitioner who performed the substantive portion, not the supervising physician by default and not whoever has the higher fee schedule rate.
3. Retain supporting documentation on file, including the signed note, time logs broken out by clinician, and the MDM elements that justify the billing decision if MDM was the method used.
4. Watch for payer-specific edits. Some Medicare Advantage plans and commercial payers layered onto Medicare rules apply their own modifier logic, so cross-check with your payer mix before assuming uniform treatment across your book of business.

A time-based claim flow looks like this: total time logged at 40 minutes, NPP contributed 24 minutes, physician contributed 16. The NPP performed the substantive portion, so the claim goes out under the NPP's NPI with modifier FS attached. An MDM-based flow looks different: the physician documents the differential diagnosis, orders the workup, and owns the final plan, even though the NPP spent more clock time with the patient. The physician bills, because the substantive part of the MDM belongs to them, not the practitioner with more minutes logged.

Confirming allowed amounts against the Physician Fee Schedule before submission catches rate mismatches that sometimes accompany incorrect NPI assignment.

Critical Care and Prolonged Services Under Split Shared Rules

Critical care never uses the MDM test. CMS keeps critical care on a time-only standard: whoever performed more than half of the total critical care time bills the service, full stop, regardless of how complex either clinician's individual decision-making was.

• Critical care time must be logged separately for each clinician, with a combined total that supports medical necessity for critical care status in the first place (typically at least 30 minutes total for the base code).
• Prolonged services attached to a split/shared E/M also rely on time. If the level of the underlying E/M was determined by time rather than MDM, the prolonged service add-on code follows the same time-based substantive-portion logic.
• Same-day E/M services billed by a different specialty, or global surgery periods overlapping the encounter, can affect whether the split/shared visit is separately billable at all. Check whether the patient already has a global period open before submitting a second E/M for the same date.

Teams that also manage telehealth-adjacent time-based coding will recognize the pattern: whenever time is the sole determinant, the documentation burden shifts almost entirely onto clean, itemized time logs rather than narrative MDM language. That's a different discipline than most EHR templates are built for, and it's worth auditing your critical care templates separately from your standard E/M templates.

Worked Examples for Time and MDM Determinations

Example 1, time-based inpatient visit. Physician logs 18 minutes, NPP logs 27 minutes, total 45 minutes. Documentation needed: separate time entries for each clinician, activity descriptions, and the NPP's signature and date.

Example 2, MDM-based ED visit. The NPP performs the initial workup and orders labs, but the physician independently reviews imaging, revises the differential, and documents the admission decision. The physician bills, because the substantive part of the MDM (the final assessment and plan) belongs to them.

The chart needs to show, in the physician's own words, the reasoning that changed the plan, not just a co-sign on the NPP's note.

Example 3, prolonged service split. A hospitalist and NPP jointly manage a complex inpatient visit totaling 65 minutes against a 40 minute threshold code.

1. Confirm which method, time or MDM, actually drove the code level before choosing your substantive-portion test.
2. Capture both clinicians' names, roles, and contributions in the note.
3. Verify the billing clinician's signature and date appear before claim submission.

Compliance and Audit Mitigation Using HIMShield Insights

Split/shared claims sit high on the audit-risk list, and the recurring failure points are predictable: missing physician signatures, time logs that don't add up to the total claimed, and templated attestation language that appears verbatim across unrelated patients.

• Missing or undated signatures on the billing practitioner's portion of the note.
• Time entries that don't reconcile between the physician's log, the NPP's log, and the total time stated in the claim.
• Generic MDM language that fails to show whose clinical reasoning actually drove the assessment and plan.
• Modifier FS omitted or misapplied on facility E/M claims that clearly involved two practitioners.

An operational checklist helps close these gaps before they become denials: a written split/shared policy, staff training tied to real chart examples, routine internal audits of a sample of split/shared claims each month, and a defined correction workflow when a gap is found before the claim goes out.

Pro Tip: Run a monthly sample audit of just your split/shared claims, separate from your general E/M audit. The failure patterns are specific enough that lumping them into a broader review lets them hide.

This is exactly the gap HIMShield's platform is built to close. It scans EHR documentation before submission, flags missing signatures, unreconciled time entries, and thin MDM language, and quantifies the at-risk reimbursement tied to each gap in a per-provider, per-payer Revenue Leakage Report. When a claim is denied anyway, having the signed note, itemized time logs, and MDM detail already assembled makes the appeal a matter of submission, not scrambling.

What Actually Matters Here

Most compliance content on split/shared billing treats the 2024 rule change as a modifier update. It isn't. The real shift is evidentiary: CMS moved the entire burden of proof onto documentation that most EHR templates were never built to capture cleanly, particularly itemized, activity-level time logs and MDM language specific enough to show whose reasoning drove the plan.

The conventional advice, "just add modifier FS and make sure someone signs the note," treats this as a checkbox exercise. It isn't. A signed note with generic attestation language and unreconciled time entries fails an audit just as fast as a claim missing the modifier entirely. The practices getting this right treat time logging as a clinical workflow change, not a coding afterthought, and they audit split/shared claims separately from general E/M claims because the failure patterns don't overlap.

If you take one thing from this guide, prioritize the time log template over the modifier. The modifier is trivial to fix. Rebuilding six months of unreconciled documentation after a payer audit request is not.

— Elena

Sources

Keep these on hand for staff training and audit responses:

• CMS Evaluation and Management Services Guide

Ready to see where your own split/shared claims stand? HIMShield's platform scans your EHR documentation for exactly these gaps, quantifies what's at risk per provider and per payer, and drafts corrections your physicians can e-sign in one click. See how it works and get your free 30-day Revenue Leakage Report before your next payer audit finds the gaps first.

This article is general information, not a substitute for advice from a qualified financial advisor. Consult a qualified financial professional about your own circumstances before acting on anything here.

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