Inpatient vs Outpatient Wound Care in SNFs: Billing Rules

Inpatient vs Outpatient Wound Care in SNFs: What You Can Bill

Skilled nursing facility wound care billing confuses even experienced billers. The rules change depending on whether the patient is in a Part A (inpatient) stay or a Part B (outpatient) status, and getting it wrong means either leaving money on the table or submitting claims that will be denied — or worse, trigger an audit.

If you run a mobile wound care practice that serves SNFs, understanding inpatient vs outpatient wound care billing is not optional. It determines which patients you can bill for, how you bill, and what documentation you need to support each claim.

This guide covers the Part A vs Part B distinction, consolidated billing rules, when outside wound care providers can bill Medicare independently, and the documentation requirements for each scenario.

Part A vs Part B: The Fundamental Distinction

Part A Inpatient Status

When a SNF patient is in a covered Part A stay, Medicare pays the facility a bundled per diem rate under the Patient Driven Payment Model (PDPM). That bundled rate is intended to cover virtually all services the patient receives during the stay, including wound care.

For outside wound care providers, the Part A rule is straightforward: you generally cannot bill Medicare separately for wound care services delivered to a patient in a covered Part A stay. The SNF's bundled payment includes wound care, and the SNF is responsible for either providing that care directly or arranging for it and paying the outside provider.

This means your financial relationship during Part A is with the facility, not with Medicare. You negotiate a rate with the SNF for wound care services, and the SNF pays you from their bundled reimbursement. This is a contractual arrangement, and the rates are typically lower than what Medicare would pay on a fee-for-service basis.

Part B Outpatient Status

When a SNF patient is in Part B status — either because they have exhausted their Part A benefit, were admitted without a qualifying hospital stay, or have been discharged from their Part A stay but remain in the facility — wound care billing changes fundamentally.

Part B patients in SNFs are treated like outpatient patients for billing purposes. Outside wound care providers can bill Medicare directly under Part B, using standard CPT codes, standard fee schedules, and standard documentation requirements. The SNF's bundled payment does not apply.

This is where most mobile wound care practices generate their SNF revenue. The Part B SNF population — residents with chronic wounds who are no longer in a covered Part A stay — represents a significant and recurring patient volume.

Consolidated Billing and Its Wound Care Exceptions

What Is Consolidated Billing?

Medicare's consolidated billing requirement means that during a covered Part A SNF stay, most services must be billed by the SNF — even if an outside provider delivers them. The SNF submits the claim and receives the payment, then pays the outside provider under their arrangement agreement.

Exclusions That Allow Independent Billing

Certain services are excluded from SNF consolidated billing, meaning outside providers can bill Medicare directly even when the patient is in a Part A stay. The exclusions most relevant to wound care include:

Physician and certain practitioner services. Physician and qualified nonphysician practitioner (NPP) professional services — including NP and PA evaluation and management services — are excluded from consolidated billing. You can bill Medicare directly for E/M services even during a Part A stay.
Certain surgical procedures. Some surgical procedures performed on SNF patients are excluded from consolidated billing and can be billed independently.

The critical nuance: while E/M services are excluded from consolidated billing, the wound care supplies and products used during those visits are generally included in the SNF's consolidated billing obligation. This means you may bill for the professional service of evaluating and treating the wound, but the skin substitute graft material, advanced dressings, and wound care supplies must be billed by the SNF.

This creates a split-billing scenario that requires careful coordination between the outside wound care practice and the SNF billing department.

When Outside Wound Care Providers Can Bill Independently

Understanding when you can bill Medicare directly is the foundation of SNF wound care economics.

During Part A Stays

E/M services (99202-99215): Billable directly to Medicare with modifier -25 when a separately identifiable E/M service is performed alongside a procedure
Professional component of procedures: Billable in some cases, but supplies and technical components typically fall under consolidated billing
Services excluded from consolidated billing: Check the current CMS exclusion list, as it is updated periodically

During Part B Status

All wound care services: Billable directly to Medicare under standard fee-for-service rules
E/M services: Standard outpatient billing rules apply
Procedures and supplies: Debridement, skin substitutes, negative pressure wound therapy, wound care supplies — all billable directly to Medicare under Part B
Place of service code: Use POS 31 (Skilled Nursing Facility) for services delivered in the SNF

The financial difference is substantial. A wound care visit during Part A might generate $75-$150 from the SNF under a contracted arrangement. The same visit during Part B can generate $150-$400 or more when billed directly to Medicare, depending on the procedure codes and payer mix.

For more on how place of service codes affect reimbursement, see Wound Care Place of Service Codes.

Documentation Requirements by Patient Status

Part A Documentation

Even though you are not billing Medicare directly during Part A, documentation standards still apply:

The SNF chart must reflect the wound care services provided
Your notes become part of the SNF's medical record and can be reviewed in a Medicare audit of the facility
If you are billing the E/M component directly (under the consolidated billing exclusion), your documentation must independently support the E/M level billed

Part B Documentation

Part B documentation follows standard outpatient wound care requirements:

Wound measurements at each visit (length, width, depth, undermining, tunneling)
Wound bed description including tissue type percentages
Medical necessity narrative explaining why the treatment provided is appropriate for this wound at this visit
LCD compliance for advanced wound care modalities — the same LCD documentation requirements that apply in any outpatient setting apply to Part B SNF visits
Treatment plan with documented goals and expected trajectory

The Verification Imperative

Before every SNF wound care visit, verify the patient's Medicare status. This sounds basic, but it is the single most common source of SNF billing errors. Patients transition between Part A and Part B status, and the transition date determines which billing rules apply to your visit.

Build a verification step into your pre-visit workflow. Confirm Part A vs Part B status with the SNF billing department before the clinician arrives. A claim submitted under the wrong billing framework will be denied, and resolving it requires resubmission under the correct pathway — if the timely filing deadline has not passed.

For a comprehensive guide to building SNF wound care referral relationships, see SNF Wound Care Partnership Model.

Structuring Your SNF Relationships

Arrangement Agreements

When you provide wound care services to Part A patients, you need a written arrangement agreement with the SNF. This agreement should specify:

Services you will provide
Compensation rates and payment terms
Billing responsibilities (who bills for what)
Credentialing and compliance requirements
Documentation and medical records access

Optimizing Your SNF Panel

The most profitable SNF relationships for mobile wound care practices involve facilities with a high proportion of Part B residents — long-term care residents with chronic wounds. These patients generate direct Medicare billing at standard fee-for-service rates, without the revenue compression of Part A contracted arrangements.

Evaluate each SNF relationship based on the Part A/Part B patient mix, wound care volume, geographic proximity to your other patients, and the facility's willingness to coordinate billing and patient access.

Key Takeaways

During Part A SNF stays, wound care services are included in the facility's bundled payment — outside providers generally cannot bill Medicare directly except for excluded professional services like E/M visits
Part B SNF residents are billed like outpatient patients, allowing mobile wound care practices to bill Medicare directly at standard fee-for-service rates using POS code 31
The financial difference between Part A contracted rates ($75-$150/visit) and Part B direct Medicare billing ($150-$400+/visit) is substantial and drives SNF practice economics
Always verify patient Part A vs Part B status before every visit — status transitions are the most common source of SNF wound care billing errors
Written arrangement agreements with SNFs are required for Part A services and should clearly define compensation, billing responsibilities, and documentation requirements