POS code 24: Ambulatory Surgical Center.

The CMS definition

A freestanding facility, other than a physician's office, where surgical and diagnostic services are provided on an ambulatory basis.

That is the description CMS publishes for POS 24, Ambulatory Surgical Center, in the Place of Service Code Set and in chapter 26 of the Medicare Claims Processing Manual. In the manual’s table it carries the Facility rate (F) designation for payment under the Physician Fee Schedule.

What it means in plain terms

POS 24 is the setting code for a freestanding surgery center that is not a physician's office and where surgical and diagnostic services are done on an ambulatory basis. The patient arrives, has the procedure and goes home the same day.

When it is used

• A physician or practitioner performs a service on a patient in a Medicare-participating ASC.
• CMS uses POS 24 as an example of a specific outpatient facility code: a practitioner who knows the exact setting where a registered hospital outpatient is treated may report that more specific code, and the manual lists POS 24 for patients registered in an ASC.

Billing implications (Medicare)

The manual marks POS 24 F, so physician fee schedule services are paid at the facility rate.

CMS adds a NOTE: practitioners who perform services in an ASC shall use POS 24 and are not to use POS 11 (office) for ASC-based services. The only exception it describes is a physician who has an office at the same physical location that meets all other office requirements, including the ASC "distinct entity" criteria, and the service was actually performed in the office suite portion of the facility.

The ASC bills its own facility fee on its own claim. POS 24 on the professional claim does not cover that fee.

The general rule in section 10.6 of the manual is that the POS code “generally” reflects the actual setting where the beneficiary receives the face-to-face service, with two exceptions: a registered hospital inpatient or outpatient is reported with the hospital code regardless of where the encounter happens. The code goes in item 24B of the paper Form CMS-1500 or the matching field of the 837P.

Look-alike codes

• POS 11: Office. Not to be used for ASC-based services except in the narrow case CMS describes.
• POS 22: On campus-outpatient hospital. A hospital department, not a freestanding facility.
• POS 19: Off campus-outpatient hospital. A provider-based department, not a freestanding ASC.

For every code in one list, with the 02 vs 10 vs 11 telehealth verdict, see the place of service code lookup.

Sources

• CMS: Place of Service Code Set — official code list and descriptions, page database updated May 2, 2024 (retrieved 2026-11-02)
• CMS: Medicare Claims Processing Manual, Chapter 26 (Rev. 12779, issued 08-09-24) — sections 10.5 and 10.6, facility and non-facility designations and special considerations (retrieved 2026-11-02)

Every definition and rule above was read from these CMS pages on November 2, 2026. Payers revise code lists, contracts and policies, so confirm anything that affects a claim with the payer. CMS itself tells billers to check each payer (Medicare, Medicaid, private plans) for how it reimburses each code.