POS 24: Ambulatory Surgical Center
POS 24 is the place of service code for an ambulatory surgical center: a freestanding facility, other than a physician office, where surgical and diagnostic services are provided on an ambulatory basis. The surgeon's claim pays the Medicare facility rate while the ASC bills its own facility fee separately.
- Setting
- Freestanding Medicare-certified surgery center
- Rate type
- Facility (lower professional payment)
- Common pairing
- Surgical CPT codes on the ASC covered procedures list
- Watch out for
- Procedures not on the ASC list leave the facility fee unpaid
What does POS 24 mean?
POS 24 identifies an ambulatory surgical center: per CMS, a freestanding facility, other than a physician's office, where surgical and diagnostic services are provided on an ambulatory basis. Patients arrive, have surgery, and go home the same day.
The code goes on the professional claims of the surgeon, assistant, and anesthesia providers for cases performed there. It signals to the payer that a separate ASC facility claim exists for the same encounter. The full POS table lives in our Place of Service reference.
When do you use POS 24?
Use POS 24 when the service was performed at a Medicare-certified (or payer-credentialed) ASC:
- Cataracts, endoscopy, arthroscopy, pain injections, hand surgery, and the rest of the outpatient surgical canon.
- Anesthesia claims for ASC cases.
- Bilateral and multiple procedures, with modifier 50 and multiple-procedure rules applied as usual.
Do not use POS 24 for hospital outpatient surgery (that is POS 22) or office-based procedures (POS 11). The certification status of the site controls, and payers can verify it against enrollment records faster than you can say recoupment.
How does POS 24 affect payment?
POS 24 puts the professional claim at the Medicare facility rate. The practice expense the surgeon would collect at POS 11 shifts to the ASC's facility payment, which is priced under the ASC payment system at rates generally lower than hospital OPPS for the same procedure. Directionally: surgeon paid less than office-based, ASC paid less than hospital, total episode cheaper than either alternative, which is exactly why payers keep steering volume to ASCs.
For physician-owners the economics run through both claims, so model cases at both rates using the Medicare fee calculator plus the ASC fee schedule before moving a procedure line from the office to the center. A procedure with high non-facility practice expense can pay the physician more at POS 11 than the combined professional-plus-distribution at POS 24.
What are the common POS 24 errors and denials?
- Procedure not on the ASC list: the ASC facility claim denies outright; scheduling should screen against the current-year list before booking.
- CARC 5 when E/M or office-only codes ride along on POS 24 claims; clarify remits with the denial code lookup.
- Global period collisions: post-op visits within the global billed without modifier 24 or 79; the global period follows the surgeon regardless of where the surgery happened.
- Mismatched claims: surgeon bills POS 24 but the ASC claim never files (or files under the wrong NPI), triggering payer development letters to both parties.
- Site-of-service misrepresentation: office procedures billed as POS 24, or ASC cases as POS 11, both of which are payment integrity flags rather than harmless typos.
Frequently asked questions
Two claims. The surgeon (and anesthesia provider) bills professional services on a CMS-1500 with POS 24 at the facility rate. The ASC itself bills the facility fee for the procedure under its own enrollment. If your practice owns the ASC, the entities still bill separately with separate NPIs and tax IDs; mixing them is an enrollment violation, not a shortcut.
Medicare maintains a list of procedures payable to ASCs, updated annually with the ASC payment system rules. If a procedure is not on the list, Medicare will not pay the ASC facility fee, though the surgeon's professional claim may still be payable. Before scheduling a new procedure type at the ASC, verify it is on the current-year list, or the facility side of the case is free work.
For procedures valued in both settings, yes: POS 24 pays the facility rate because the ASC bears the room, staff, and supply costs. For office-capable procedures the non-facility rate at POS 11 can be substantially higher to the physician, but the ASC setting adds the separate facility payment. Where a case belongs is a clinical and economic decision; the POS code just has to tell the truth about it.
POS 11, and the physician collects the full non-facility rate with no facility fee. An office procedure room is not an ASC no matter how well equipped, unless it is separately certified and enrolled as one. Billing POS 24 from a non-certified office suite is misrepresentation; billing POS 11 from a certified ASC forfeits the facility fee and misprices the professional claim.
Sources & further reading
Reviewed by the ImmediCare Solutions RCM team
Certified billers and coders handling claims across 50+ specialties nationwide. This entry is reviewed against current payer policy and CMS rules. Last review: Jul 5, 2026.
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