POS 31 is a Place of Service (POS) code used on professional claims to identify medical services performed for a patient receiving a covered Medicare Part A stay in a Medicare-certified Skilled Nursing Facility (SNF).

POS 31 is the primary billing designation for skilled nursing care, rehabilitation services, and physician encounters delivered in an inpatient SNF setting.

Medical providers report POS 31 on the CMS-1500 claim form to ensure accurate reimbursement, compliance with CMS billing rules, and proper facility-rate payment calculations.

Accurate POS 31 reporting supports clean claims, prevents denials, and aligns professional services with current CMS and Medicare Claims Processing Manual requirements.

This guide covers what POS 31 means, when to use POS 31, Skilled Nursing Facility requirements, Medicare Part A coverage rules, POS 31 vs POS 32, reimbursement implications, common billing mistakes, and best practices for accurate SNF claim submission.

What Qualifies as a Skilled Nursing Facility?

A Skilled Nursing Facility is a Medicare-certified inpatient facility that provides skilled nursing care, rehabilitation, and related services to patients who need professional medical or nursing services but do not need hospital-level care. The facility must meet specific CMS standards to keep its certification.

To qualify, a facility must offer:

24-hour licensed nursing services
Physician supervision
Skilled rehabilitation services such as physical, occupational, or speech therapy
Medical social services and care planning
Pharmacy services and medication administration
A safe physical environment that meets life-safety code

Medicare-certified SNFs are surveyed regularly by state agencies under contract with CMS. The facility’s certification is what allows it to bill Medicare Part A for short-term post-acute care.

What’s the Difference Between an SNF and a Nursing Home?

A skilled nursing facility gives short-term medical and rehabilitative care after a hospital stay. A nursing home, in everyday use, often means a long-term custodial care setting. The two terms get mixed up because many facilities offer both types of care under one roof.

The differences matter for POS selection:

Skilled care treats medical conditions that require licensed nursing or therapy. It is covered by Medicare Part A after a 3-day qualifying inpatient hospital stay, up to 100 days per benefit period.
Custodial care helps with daily activities like bathing, dressing, and eating. It is not covered by Medicare. Most custodial care is paid by Medicaid (with state-level eligibility rules) or private funds.

A single building may have residents in Part A skilled stays (bill POS 31) and residents in long-term custodial stays (bill POS 32) at the same time. CMS calls these mixed facilities. In a mixed facility, the correct code depends on each patient’s Part A coverage status on the date of service, verified per patient rather than applied building-wide.

Is POS 31 Inpatient or Outpatient?

POS 31 is an inpatient code. A patient in a covered SNF stay is classified as an inpatient of the facility, even though SNF care is not the same as hospital inpatient care. The patient lives in the facility, gets care under physician orders, and receives 24-hour nursing supervision.

The inpatient classification matters because:

Physician services are paid at the facility rate, not the office rate.
The SNF itself bills Medicare Part A under the SNF Prospective Payment System for the per-diem stay.
Practitioners bill Medicare Part B separately for professional services using POS 31.

A common point of confusion is between Part A coverage (which decides POS 31 versus POS 32) and the inpatient label itself. A patient can be an inpatient of a nursing facility under POS 32 too, but only POS 31 carries an active Part A skilled stay.

If the same patient leaves the SNF and visits the physician’s office, the office visit is billed with POS 11 (Office), not POS 31. The code follows where the face-to-face service happened, with one important exception: under CMS guidance, if a physician sees an SNF inpatient inside the physician’s office during the Part A stay, the inpatient status still governs, and POS 31 is the correct minimum code.

Is POS 31 a Facility or Non-Facility?

POS 31 is a facility setting under Medicare’s payment structure. This designation is set in the CMS Medicare Claims Processing Manual and reflected in the CY 2026 Physician Fee Schedule Final Rule (CMS-1832-F), issued October 31, 2025.

Facility status changes the practice expense (PE) component of the Relative Value Units (RVUs) that build each payment. In a facility setting, CMS assumes the facility itself absorbs overhead like exam rooms, basic supplies, and clinical staff time, so the PE portion of the physician’s payment is reduced.

The CY 2026 Final Rule changed the PE methodology in a way that affects POS 31. CMS finalized a policy that reduces the portion of facility PE RVUs allocated based on work RVUs to half the amount allocated to non-facility services for the same code. Historically, nursing facility E/M codes (such as CPT 99304-99310) carried the same indirect PE per work RVU in facility and non-facility settings.

Beginning January 1, 2026, services billed with POS 31 receive a lower PE-adjusted payment than the same code billed with POS 32. PALTmed estimated a roughly 6% reduction for CPT 99309, the most commonly used subsequent nursing facility visit code, under the new methodology.

As a result, the same E/M code can reimburse differently depending on whether it is billed with POS 31 or POS 32, which makes accurate verification of the patient’s coverage status part of a clean claim submission.

When Should You Use POS 31?

Use POS 31 when the patient has an active Medicare Part A SNF benefit at the time of the service. The patient must be inside the 100-day Part A benefit window, and the facility must be Medicare-certified.

Common scenarios that warrant POS 31:

A physician makes a subsequent visit (CPT 99307-99310) to a patient who was admitted to the SNF five days ago after a 4-day inpatient hospital stay for a hip fracture.
A wound care specialist treats a stage 3 pressure ulcer for a patient on day 15 of a covered SNF stay following pneumonia.
A psychiatrist evaluates a stroke patient for post-stroke depression on day 22 of the patient’s Part A stay.
A cardiologist conducts a follow-up telehealth visit (with modifier 95 and the SNF’s address) for a patient still inside the Part A window.

Documentation needed to support POS 31:

Proof of a qualifying 3-day inpatient hospital stay (admission and discharge dates)
SNF admission date within 30 days of hospital discharge
Physician certification of skilled need
Daily nursing notes showing skilled services
Verified Part A days remaining

If any of these elements are missing or the Part A days have run out, POS 31 is not the right code.

POS 31 vs POS 32: What’s the Difference?

The difference comes down to one question: does the patient have an active Medicare Part A SNF benefit on the date of service? If yes, use POS 31. If no, use POS 32.

POS 32 applies to:

Patients in a long-term care or custodial nursing facility from day one
Patients in an SNF who have used all 100 Part A days
Patients in an SNF whose stay does not meet Part A coverage rules (no 3-day prior hospital stay, no skilled need, and so on)

The deciding factor is not the building. It is the patient’s coverage status on the date of the encounter. A patient who started in a covered Part A SNF stay on POS 31 may roll over to POS 32 once Part A coverage ends, even if the patient never leaves the same building.

Factor	POS 31 (SNF)	POS 32 (Nursing Facility)
Patient stay type	Active Medicare Part A skilled stay	Long-term custodial stay, or SNF after Part A exhausted
Required hospital stay	3-day qualifying inpatient stay	None
Facility classification (CMS)	Facility setting	Non-facility setting
Payment rate historically	Lower (facility PE)	Higher (non-facility PE)
CY 2026 PE methodology impact	Lower PE-adjusted payment	Higher PE-adjusted payment than POS 31
Common E/M codes	99304-99310, 99315-99316	99304-99310, 99315-99316
Coverage source	Medicare Part A (per-diem)	Medicare Part B, Medicaid, private pay
100-day cap	Yes (per benefit period)	No

How Do You Bill POS 31 Correctly?

Quick-reference billing checklist for POS 31:

Part A days verified for this date of service
Qualifying 3-day inpatient hospital stay on file
SNF admission within 30 days of hospital discharge
The facility is Medicare-certified
Skilled need documented in physician orders and nursing notes
Correct CPT code selected (99304-99318 range)
Modifiers applied correctly (95 for telehealth, and others as applicable)
POS 31 entered in Box 24B
Service location address matches the SNF
NPI of the rendering provider on the claim

What Are the Most Common POS 31 Billing Errors?

Top POS 31 related errors to watch for:

Using POS 32 during an active Part A stay: This is the error the CMS system edit under CR 13767 targets. The claim either rejects or gets recouped after the fact.
Continuing POS 31 after Part A coverage ends: The patient may stay in the same room and the same bed, but once the 100-day Part A benefit is used up or skilled need ends, POS 31 is no longer correct.
Wrong POS on transfer days: A patient transferring from the hospital (POS 21) to the SNF (POS 31) on the same calendar day creates a date-of-service question. Match the POS to where the patient was at the time of the face-to-face encounter.
Billing under the wrong NPI: Some practices bill SNF services under a group NPI that does not have privileges at the facility, which creates credentialing denials before the POS even matters.
Missing the modifier on telehealth visits: A virtual visit to an SNF patient still needs modifier 95 (synchronous audio-video) to identify the visit as telehealth, even when POS 31 is correct for the patient’s location.
Mixed facility errors: In a building that houses both SNF and long-term care residents, defaulting to one code for all patients leads to errors. Verify status for each patient at each visit.

Final Words

Two recent changes make accurate POS 31 coding more important than before: the July 2025 CMS system edit under CR 13767, which flags POS 32 used during an active Part A stay, and the CY 2026 PE methodology that applies different practice expense values to POS 31 and POS 32.

The workflow is simple. Verify Part A status before every visit. Match the POS code to the patient’s actual coverage on the date of service. Document the skilled need. Build a pre-billing checkpoint so POS 31 claims do not move forward without a verified Part A flag.