POS 24 — Ambulatory Surgical Center: Place of Service Code Explained

POS 24: What It Identifies

POS 24 identifies procedures performed in a Medicare-certified ambulatory surgical center — the freestanding surgery centers where a growing share of outpatient procedures now happen. Professional claims carry POS 24 while the ASC bills its own facility claim, and the coverage rules differ from hospital settings in ways that surprise practices.

Use POS 24 For

Surgeon and anesthesia professional claims for ASC procedures
Procedures on the payer's ASC-approved list performed in a certified ASC
Physician-owned surgery center cases (with ownership disclosure rules honored)

Don't Use It For

Office procedure rooms — POS 11, even for the same CPT codes
Hospital outpatient surgery — POS 22
Procedures NOT on the payer's ASC list — coverage may fail entirely at POS 24

How POS 24 Affects Payment

Professional claims pay facility rates at POS 24; the ASC bills its facility fee under the ASC payment system. The trap is coverage, not just rate: payers maintain ASC-approved procedure lists, and scheduling a procedure at the ASC that the payer only covers in hospitals produces denials that no coding fixes. Verify site-of-service coverage during scheduling.

Common POS 24 Billing Errors

ASC cases billed POS 11 or 22 by template default
Procedures scheduled at the ASC without checking the payer's site-of-service list
Anesthesia claims mismatching the surgeon's POS — payers cross-check the case's claims against each other

ASC vs Hospital Outpatient: Why the Same Surgery Pays Differently

An ambulatory surgical centre and a hospital outpatient department can perform an identical procedure with the same surgeon, and Medicare will pay two noticeably different facility amounts. The reason is that they sit under two separate payment systems: ASCs are paid under the ASC payment system, while hospital outpatient departments are paid under OPPS. The ASC rate is generally the lower of the two.

	POS 24 — ASC	POS 22 — hospital outpatient
Facility payment system	ASC payment system	OPPS
Typical facility rate	Lower	Higher
Procedure eligibility	Must be on the ASC covered procedures list	Broader range permitted
Your professional fee	Billed separately, facility rate	Billed separately, facility rate

Check the covered procedures list before you schedule. Medicare pays an ASC facility fee only for procedures on its covered procedures list. Schedule something that is not on it and the facility side simply does not get paid — which is a scheduling failure, not a billing one, and no appeal fixes it after the fact.

The second thing that catches people is packaging. A substantial amount is bundled into the ASC rate rather than being separately payable — most drugs and supplies used in the procedure, anaesthesia materials, and routine equipment. Billing those separately produces bundling denials rather than extra revenue.

Consolidated billing exclusion lists and covered-procedure lists are updated by CMS annually — verify the current year's list before relying on any specific service category.

Your professional fee is billed separately and paid at the facility rate, because the ASC is carrying the overhead. That is the same logic that makes POS 11 pay more — there, you carry the overhead yourself. If you are unsure which setting applies, the POS decision tree walks it through.

Related POS Codes

POS 22 — On-campus outpatient POS 11 — Office POS 19 — Off-campus outpatient

← Back to the full POS code reference

Reviewed by Hassan Raza Awan, Founder — 4+ years of hands-on U.S. medical billing experience. General billing information — verify against current CMS guidance and your payer contracts.

Frequently Asked Questions

The same procedure pays differently at POS 11, 22, and 24?

Yes — three different payment constructions. In office (11), the physician's non-facility rate covers everything. At the ASC (24) and hospital (22), the physician gets facility rates while the ASC or hospital bills its own fee under different systems. Total cost and patient share differ at each site, which is why payers increasingly steer site of service.

Why did a routine procedure deny entirely at our ASC?

Probably the payer's ASC-covered list — some procedures are covered only in hospital outpatient settings per policy. It's a coverage rule, not a coding error, and the fix is front-end: verify site-of-service coverage when scheduling, not after the denial.

Why does an ASC pay less than a hospital outpatient department?

They sit under two separate Medicare payment systems. Ambulatory surgical centres are paid under the ASC payment system, while hospital outpatient departments are paid under OPPS, and the ASC facility rate is generally the lower of the two for the same procedure.

What is the ASC covered procedures list?

Medicare pays an ASC facility fee only for procedures on its covered procedures list. If a procedure is not on the current list, the facility side is not paid - which makes it a scheduling decision rather than a billing one, because no appeal recovers it afterwards.

POS 24: Ambulatory Surgical Center