POS 13 Medical Billing: The Assisted Living Facility Place of Service Code

POS 13 (Assisted Living Facility) is the two-digit place of service code that tells a payer the service was rendered in an assisted living facility. CMS defines the setting as a congregate residential facility with self-contained living units that assesses each resident's needs, has 24-hour on-site availability of support, and provides supervision, safety, and security plus personal-care assistance and coordination of medical services. The defining line is care intensity: assisted living supports activities of daily living, but it is not a skilled nursing facility and does not provide the skilled nursing or rehabilitation services that move a patient into POS 31 or POS 32.

The POS code lives in Box 24B of the CMS-1500 form and Loop 2300 CLM05-1 of the 837P. It does two jobs: it tells the payer which fee schedule to apply (non-facility or facility), and it documents where care happened, which feeds coverage, medical-necessity, and provider-enrollment edits. POS 13 belongs to the residential POS family (Home, Assisted Living, Group Home, Custodial Care) rather than the institutional family (SNF, Nursing Facility, Inpatient Hospital), and that family membership drives both the rate and the correct E/M code set.

In our setting-of-care audits we typically see assisted living visits coded with office E/M codes far more often than the reverse — a coder applying 99213 out of habit instead of the home-or-residence code the residential POS requires. That single mismatch is the most common reason a clean POS 13 visit still denies.

POS 13 is used by practitioners who travel to the patient — the encounter happens at the resident's assisted living address, not in a clinic. The most common billers are:

• House-call and home-based primary care groups rounding on a panel of assisted living residents.
• Geriatricians, internal medicine, and family practice physicians managing chronic conditions on-site.
• Nurse practitioners and physician assistants under their own NPI or incident-to rules — the bulk of facility rounding for many groups.
• Behavioral health and psychiatry providers seeing residents for medication management or therapy.
• Podiatry, wound care, and mobile diagnostic providers delivering specialty services on-site.

Use POS 13 when all of the following are true: the patient's residence is an assisted living facility (not a nursing facility, private home, or group home), the service was performed at that address, and the rendering provider is enrolled with the payer for that service location. If the patient lives in assisted living but you saw them in your office, the visit is POS 11 (Office) with office E/M codes — the POS follows where the encounter physically occurred, not where the patient lives.

Many of these visits also support care-coordination billing: a practitioner managing multiple chronic conditions may layer Chronic Care Management or Transitional Care Management on top of the visit when documentation and time requirements are met. Outsourced medical coding services frequently catch missed CCM/TCM revenue on exactly this patient mix.

Every CPT code on the Medicare Physician Fee Schedule (MPFS) carries two payment amounts: a non-facility rate and a facility rate. The difference is the practice-expense RVU. In a non-facility setting the practice bears the overhead — staff, supplies, space — so CMS pays a higher practice-expense component. In a facility setting an institution (hospital, ASC, SNF) bears that overhead and bills its own facility fee, so CMS pays the physician a reduced component. For the same CPT the non-facility rate is typically 10-30% higher than the facility rate, varying by code (source: CMS PFS methodology).

POS 13 maps to the non-facility rate. Assisted living is treated like the patient's home for fee-schedule purposes — the practitioner brings their own resources and no separate institutional facility fee is billed. This is the single most important reimbursement fact about POS 13: miscoding the visit as a facility POS (for example POS 31 SNF, which is facility) can quietly underpay every visit.

The table below shows how the residential and nursing POS codes split between the two rate buckets. The pattern is the trap — the residential codes are uniformly non-facility, the nursing codes are split, and the split does not follow intuition.

Note the two surprises practitioners miss most. First, under the 2026 Medicare Physician Fee Schedule, CMS adjusted the practice-expense RVUs so that POS 32 (Nursing Facility) is paid on non-facility PE RVUs while POS 31 (Skilled Nursing Facility) is paid on facility PE RVUs — historically the two carried identical PE RVUs, so this split is recent and worth re-confirming each year (source: CMS PFS 2026 final rule). Second, although POS 31 and 32 share the same nursing-facility E/M code family (99304-99316), POS 13 does not — assisted living uses the home-or-residence codes. Confirm the exact rates for your CPTs and locality in the current CMS PFS lookup; bands here describe the structure, not a fixed dollar.

The residential and nursing POS codes look interchangeable on a worklist, but each carries a specific definition, rate basis, and E/M code set. Getting them right starts at scheduling — where residence type is captured — not at billing.

The most consequential pairings to keep straight:

• POS 13 vs POS 32. Both non-facility, so the rate is the same — but the E/M family differs (99341-99350 vs 99304-99316). Crossing them is a setting/code mismatch denial.
• POS 31 vs POS 32. Same E/M family (99304-99316). Under the 2026 PFS, POS 31 (SNF/Part A skilled) is paid on facility PE RVUs while POS 32 (NF) is paid on non-facility PE RVUs — a recent split (the two were historically equal), so the more intensive SNF setting now pays the practitioner less per code because the SNF carries the overhead and bills Part A. Re-confirm against the current fee schedule each year.
• POS 13 vs POS 12. Both non-facility, both home/residence E/M family — the practical distinction is the residence type and address on file with the payer. A POS that contradicts that record can trigger an information or eligibility edit.

The operational fix is the same across all six: capture residence type as a structured field at scheduling, map it to the correct POS in the PM system, and apply the POS automatically rather than relying on the coder to remember the chart. For the office-vs-hospital side of the POS map (POS 11, 19, 22) and telehealth (POS 02, 10), see our companion place of service codes guide.

Services in an assisted living facility are billed with the Home or Residence Services E/M codes, range 99341-99350. The code set changed recently, and a lot of templates and superbills are still out of date.

Effective January 1, 2023, CMS and the AMA deleted the Domiciliary, Rest Home, or Custodial Care codes 99324-99337 and folded those services into the home-or-residence family. Before 2023 an assisted living visit was often coded 99324-99337 (domiciliary); after 2023 the same visit is coded:

• New patient: 99341, 99342, 99344, 99345 (99343 was deleted in the renumbering).
• Established patient: 99347, 99348, 99349, 99350.

Like all E/M visits since the 2021/2023 reforms, level selection is based on medical decision making (MDM) or total time on the date of the encounter — not the old history/exam bullet counts. The home-or-residence codes carry their own time thresholds, distinct from office thresholds, so a practitioner billing on time must use the home-visit bands, not the 99202-99215 bands.

The practical error to watch for: a practice migrates a patient from clinic to assisted living rounding, but the EHR template still suggests 99213/99214 (office). Those codes paired with POS 13 produce a setting/code mismatch. Default facility-rounding templates to the 99341-99350 family, and retire any superbill that still lists 99324-99337 — those codes no longer exist and will reject.

POS 13 visits draw a recognizable cluster of denials. The codes below are X12 Claim Adjustment Reason Codes (CARC); the Group Code prefix (CO = Contractual Obligation provider write-off, PR = Patient Responsibility) tells you whether the balance can move to the patient.

The single biggest POS 13 root cause is the setting/code mismatch — an office E/M (99202-99215) billed with a residential POS, or a residential POS paired with the wrong E/M family. It surfaces as CO-16, CO-4, or CO-58 depending on the payer's edit logic, which makes one problem look like several. Default facility-rounding encounters to 99341-99350 at the template level and the cluster collapses.

The second-biggest is enrollment/credentialing (B7) — a new NP or PA added to a rounding panel before enrollment for that location is active. This is a timing problem, not a coding one; hold the claims or bill under a properly enrolled supervising provider per incident-to rules until enrollment posts.

For CO-97, the question is whether the visit was a separately identifiable service or a component of a same-day procedure; when genuinely distinct, the fix is a documentation-supported modifier (full decision tree in our 97 denial code guide). For the broader library, see the CARC denial codes list.

A defensible POS 13 claim is built at the encounter, not reconstructed at appeal. Confirm each item before the claim drops:

1. Residence type verified — the patient genuinely resides in assisted living, not a nursing facility, group home, or private home. Capture it as a structured scheduling field, not free text.
2. Service location address documented and tied to the provider's enrolled service location with the payer.
3. Correct E/M family — coded 99341-99350 (home/residence), not 99202-99215 (office) or 99304-99316 (nursing facility); any superbill listing 99324-99337 retired.
4. Level supported by MDM or time on the date of service, using the home-visit time bands.
5. Provider enrolled for the location — the rendering NP, PA, or physician is credentialed and enrolled with the payer; incident-to billing, if used, meets supervision rules.
6. Medical necessity supported — the diagnosis justifies a residence visit rather than an office visit.
7. Care-coordination add-ons captured — CCM/TCM billed alongside the visit when time and documentation requirements are met.
8. POS applied at the location level so a rotating provider cannot carry an office POS into a facility visit.

Practices that capture residence type at scheduling and configure POS at the location level — rather than asking coders to remember it — see the POS 13 denial cluster shrink, because the most common error (setting/code mismatch) is engineered out of the workflow rather than caught after the fact.

POS 13 is a small field with an outsized effect on home-based and facility-rounding revenue. Three disciplines keep it clean:

1. Capture residence type upstream. The choice among POS 12, 13, 14, 32, and 33 is a fact about where the patient lives — it should be a structured field captured at scheduling, not a guess at the billing desk. Most setting/code mismatch denials trace back to this fact never being captured cleanly.
2. Map POS at the location level, not the encounter level. Configure the PM system so an encounter at a registered assisted living location automatically carries POS 13 and prompts the 99341-99350 family. Manual POS entry by rotating providers is the single largest source of drift.
3. Tie enrollment to the rounding panel. Every practitioner must be enrolled with each payer for each service location before seeing patients there, or their visits deny B7. Build an enrollment check into onboarding for any provider added to a facility panel.

Get those three right and POS 13 becomes a non-event: the right rate, the right code family, and the right enrolled provider on every claim. If your team is rounding on assisted living patients but losing visits to setting/code mismatches, enrollment gaps, or under-coded levels, outsourced medical billing services and denial management can own the POS mapping, code-family alignment, and appeals end to end.