ASC billing: the covered procedures list, device payment, and the claim form question

THE BOTTOM LINE

An ASC is not a physician office and not a hospital, and almost every ASC billing rule follows from that. Treat an ASC claim like either one and the denials will tell you so.

Four things drive most of the preventable loss: procedures billed without confirming they are on the covered procedures list, implants billed as separately payable when they are packaged, the multiple procedure reduction not applied before submission, and place of service coded as a hospital outpatient department.

CY 2026 is also an unusually large year for the covered procedures list. If you have not re-checked your procedure mix against it since January, that is the highest-value thing on this page.

Definitions and frequently used terms

ASC CPL. ASC Covered Procedures List. The list of surgical procedures Medicare will pay an ASC facility fee for. If a procedure is not on it, Medicare does not pay the facility fee, no matter how appropriate the case was.

APC. Ambulatory Payment Classification. The grouping structure used to set rates. The ASC system uses the same relative weights as hospital outpatient but applies its own conversion factor.

IPO list. Inpatient Only list. Procedures Medicare covers only in an inpatient hospital setting. Currently being phased out, which matters for planning.

Pass-through device. A device with temporary separate payment above the bundled rate, identified by a C-code.

Packaged device. A device whose cost is built into the procedure payment. Not separately billable.

Device offset. The portion of a procedure's payment that CMS attributes to the device. This is the number that determines device-intensive status.

Device-intensive procedure. A procedure whose device offset exceeds 30% of the procedure's mean cost.

ASCQR. ASC Quality Reporting program. Meeting its requirements gets you the full annual rate update. Missing them costs you most of it.

CARC and RARC. Claim Adjustment Reason Code and Remittance Advice Remark Code. The CARC gives the category, the RARC the detail.

Which claim form, and the facility versus professional split

This gets asked constantly and the answer is short.

ASCs bill Medicare using the ASC X12 837 professional format, or in rare cases the paper CMS-1500. Not the UB-04 or 837 institutional format. Medicare Claims Processing Manual Chapter 14 is explicit: an ASC "bills the Medicare contractor using the ASC X12 837 professional claim format or, in rare cases, on Form CMS-1500."

That surprises people, because an ASC feels institutional. For Medicare billing purposes it is not.

NOTE: some commercial payers do want ASC facility claims on a UB-04 or 837I. That is a contract-level question, not a Medicare question, and it is worth confirming per payer rather than assuming your Medicare setup carries over.

Two separate claims go out for the same case:

1. The facility claim, under the ASC's NPI and Tax ID, covering the operating room, nursing staff, anesthesia monitoring (not the anesthesiologist's professional service), supplies, equipment, and separately payable implants.
2. The professional claim, under the operating surgeon's own NPI.

Both carry the same date of service and the same CPT codes, and both can go out without triggering a duplicate denial, because they are different providers billing non-overlapping work.

Place of service

POS 24 is a freestanding ambulatory surgery center. POS 22 is an on-campus hospital outpatient department. Every line on a standard ASC claim should carry POS 24.

IMPORTANT, because the usual explanation of this is mechanically wrong: submitting an ASC facility claim with POS 22 does not cause Medicare to pay you hospital outpatient rates. A freestanding ASC is paid under the ASC fee schedule based on its enrollment and provider type, not based on the POS code you submit. You cannot code your way into OPPS payment.

What a wrong POS actually produces is an edit or a denial, commonly CARC 5 ("The procedure/revenue code is inconsistent with the place of service") or CARC 171 ("Payment is denied when performed/billed by this type of provider in this type of facility"), plus incorrect patient cost-sharing, which is its own compliance problem.

Put a validation rule in front of submission that checks POS against the facility NPI type. It is a one-time build.

What changed for CY 2026

CMS issued the CY 2026 OPPS/ASC Final Rule (CMS-1834-FC) on November 21, 2025, published in the Federal Register November 25, 2025, effective January 1, 2026. It reaches more than 6,300 Medicare-certified ASCs.

Three things matter operationally, and one of them is much bigger than the coverage it usually gets.

The rate update

CMS finalized a 2.6% update to ASC rates for CY 2026, built from a 3.3% hospital market basket increase less a 0.7 percentage point productivity adjustment. That applies to ASCs meeting ASCQR requirements.

ASCs that do not meet ASCQR reporting get 0.6% instead. In conversion factor terms that is $56.322 for compliant ASCs versus $55.224 for non-compliant. It is worth knowing the actual gap rather than "a reduced update," because it makes the quality reporting conversation concrete.

No claim form change is required, but expected-payment tables and underpayment variance reports need recalibrating against the new schedule.

The covered procedures list, which grew by 560

IMPORTANT: CMS added 560 procedures to the ASC CPL for CY 2026. The CMS fact sheet gives it in two parts: 289 procedures added to the CPL, plus 271 codes added because they came off the inpatient-only list.

I am being emphatic about the number because a figure of 302 has circulated widely and it does not correspond to anything in the final rule. It is not the total, not the criteria-based subset, and not the IPO transfers. If your planning was built on 302, you have roughly half the expansion unaccounted for, which means procedures you could be doing and billing are sitting on a list nobody re-checked.

CMS also revised the eligibility criteria at 42 CFR 416.166 for evaluating whether a procedure is appropriate for the ASC setting. Procedures can also be added in response to stakeholder comment during the annual rulemaking cycle, which is how a portion of this year's additions got there. If there is a procedure your surgeons perform routinely and safely that is not on the list, the comment period is the mechanism, and it does work.

The current CPL is in Addendum AA of the final rule and on the CMS ASC payment system page. CMS publishes quarterly payment update transmittals that add and terminate codes and rates.

SAVE this as a recurring task: assign one person to re-check the CPL against your actual procedure mix at the start of each calendar year and at each quarterly release. In a year like this one, that check is worth real money.

The inpatient-only list is going away

This is the structural change the CY 2026 rule is remembered for, and it is often left out of billing summaries entirely.

CMS finalized a three-year phase-out of the inpatient-only list, beginning with 285 mostly musculoskeletal procedures removed for CY 2026. The CY 2027 proposed rule continues it with a second, larger tranche, which puts the final year at CY 2028.

Two things follow. First, the IPO list is not a stable fixture you can check once and forget. Second, coming off the IPO list does not automatically put a procedure on the ASC CPL. The CY 2026 numbers prove it: 285 came off the IPO list and 271 of those went onto the ASC CPL, leaving a 14-code gap. You have to check both lists separately before scheduling.

Device and implant payment

This is where the most money moves per error, so it gets its own section.

Pass-through versus packaged

Pass-through devices carry a temporary HCPCS C-code and are separately payable above the bundled procedure rate. Under 42 CFR 419.66(g), pass-through eligibility runs at least 2 years but not more than 3 years from the first date pass-through payment is made. The commonly repeated "three years" is the ceiling, not the rule.

Packaged devices are built into the procedure payment and are not separately billable. Putting one on its own line generates CARC 96 ("Non-covered charge(s)").

Devices rotate. A device that had an active C-code last year may be packaged this year. The January 2026 update, for example, added C1607 and C1608 effective January 1, 2026, while pass-through for C1826, C1827, and C1747 expired December 31, 2025.

SAVE: at every CMS quarterly release, one person compares last quarter's pass-through list to this quarter's and updates the device charge master. Devices that rotated off need their C-code retired. Devices newly approved need one added. A device billed with a retired C-code denies every single time until someone fixes the charge master, which means the denial repeats until the process changes rather than until someone works the claim.

Device-intensive procedures and the device offset

A procedure is device-intensive when its device offset exceeds 30% of the procedure's mean cost.

NOTE on how that gets calculated, because this is usually described wrong: CMS derives the device offset percentage from claims data at the HCPCS code level, not from facility cost reports. For the CY 2026 rule the basis was CY 2024 claims. Device-intensive designations appear in the ASC Addenda files.

For device-intensive procedures the specific device HCPCS code has to appear on the claim so the payer can verify device eligibility for the enhanced rate. When a device-intensive procedure gets added to your schedule, the device code mapping has to be added to the charge master at the same time, not later.

IMPORTANT: a missing device HCPCS code is not a modifier problem and will not come back as CARC 4. CARC 4 is "The procedure code is inconsistent with the modifier used," which requires a modifier to be present and mismatched. A missing device code produces a pricing shortfall or a non-covered or return-to-provider edit instead. Filing this under CARC 4 sends your team looking for a modifier that was never the issue.

The multiple procedure reduction

When two or more covered surgical procedures happen in the same operative session, Medicare pays 100% of the highest-paying procedure and 50% of the applicable rate for each additional procedure. Claims Processing Manual Chapter 14 states it directly: contractors "pay 100 percent of the highest paying surgical procedure on the claim, plus 50 percent of the applicable payment rate(s) for the other ASC covered surgical procedures."

This applies to the facility fee. The surgeon's professional fee is subject to a separate multiple procedure reduction under the physician fee schedule.

NOTE on the CARC: the code that reports a multiple or concurrent procedure adjustment is CARC 59, "Processed based on multiple or concurrent procedure rules." It is not CARC 45. CARC 45 is "Charge exceeds fee schedule/maximum allowable or contracted/legislated fee arrangement," which is a generic allowed-amount write-down and describes a different thing entirely. If your denial taxonomy has multiple procedure reductions filed under 45, that is worth correcting, because it will make your variance reporting look like a contracted-rate problem when it is a payment-rule problem.

IMPORTANT, and this is an open item rather than an instruction: the flat 50% does not apply uniformly to device-intensive procedures, because the device portion is treated differently from the service portion. Before you build a variance report that applies a flat 50% to every secondary procedure, check the payment indicators in Addenda AA and BB for your device-intensive cases. Otherwise the report will flag correctly-paid claims as underpayments and your team will spend days chasing them. I have not been able to work through the current addenda to give you the exact treatment, so I would rather flag it than guess.

Prior authorization: the ASC demonstration

There are two different CMS prior authorization programs in this space and they get conflated. The one that applies to you is the ASC demonstration, not the hospital outpatient department model. The HOPD program is nationwide and is not administered state by state, so anything describing a state-by-state expansion is not describing it.

The Prior Authorization Demonstration for Certain Ambulatory Surgical Center Services covers five categories:

1. Blepharoplasty, blepharoptosis repair, and brow ptosis repair
2. Botulinum toxin injection
3. Panniculectomy
4. Rhinoplasty
5. Vein ablation

It rolled out in two phases after a delay from an originally planned December 2025 start:

• Phase 1 states (California, Florida, Tennessee, Pennsylvania, Maryland, Georgia, New York): requests accepted from January 5, 2026, for dates of service on or after January 19, 2026.
• Phase 2 states (Texas, Arizona, Ohio): requests accepted from February 2, 2026, for dates of service on or after February 16, 2026.

If you are in one of those ten states and you do any of those five procedure categories, that is directly actionable today.

Separately, commercial payers require authorization for many ASC procedures on their own terms. CARC 197 ("Precertification/authorization/notification/pre-treatment absent") at an ASC usually means one of three things: nothing was submitted, the authorization covers the wrong procedure code, or it expired before the date of service.

Build a per-payer authorization matrix for your 20 highest-volume procedures, put it where scheduling staff can see it, and review it at each contract renewal. Verification belongs in pre-surgical clearance, not after the case is on the schedule.

Modifier SG

CMS dropped the SG modifier requirement for Medicare ASC facility claims effective January 1, 2008, per Claims Processing Manual Chapter 14: "Beginning January 1, 2008, ASCs no longer are required to include the SG modifier on facility claims in Medicare."

Some commercial payers still require it as a condition of adjudication. Verify at credentialing and at contract renewal, because omitting it where it is required can produce a modifier-mismatch denial or a general non-covered adjustment.

The denial patterns you will actually see

These are the recurring patterns rather than a ranked list. I do not have published frequency data for ASC denials specific enough to rank them honestly, and I would rather say that than invent an order.

Procedure not on the ASC CPL (CARC 96, CARC 204)

CARC 96 is "Non-covered charge(s)." CARC 204 is "This service/equipment/drug is not covered under the patient's current benefit plan."

Medicare does not pay an ASC facility fee for a procedure outside the approved list. This also hits when a procedure was on last year's list and was removed or reassigned.

Prevention is pre-scheduling verification, not billing verification. Check the primary CPT code against the current CPL and the IPO list before the case is confirmed, while there is still time to redirect it. That check takes under two minutes with the Addendum AA file open, and it happens before the patient gets a financial estimate, a prep appointment, or an anesthesia consult.

Implant misclassified (CARC 96)

Two versions. A packaged implant billed on its own line, or a pass-through device billed with an expired or incorrect C-code. Both come back as CARC 96 and both trace to the charge master rather than to the biller.

Multiple procedure reduction not applied (CARC 59)

Apply the reduction in your billing system before submission so the billed amount matches the expected adjusted amount. Many PM systems have ASC multiple procedure logic available; confirm it is switched on and that it handles your actual procedure combinations rather than just the simple two-code case.

Place of service mismatch (CARC 5, CARC 171)

Covered above.

Device code missing on a device-intensive procedure

Produces underpayment because the payer cannot verify device eligibility for the enhanced rate. Not a CARC 4 situation, per the note above.

Prior authorization absent (CARC 197)

Covered above.

Concurrent or incompatible procedures (CARC 236)

CARC 236 is "This procedure or procedure/modifier combination is not compatible with another procedure or procedure/modifier combination provided on the same day according to the National Correct Coding Initiative or workers compensation state regulations/fee schedule requirements."

Read that definition carefully, because it is explicitly sensitive to the modifier combination. "Mutually exclusive" is legacy NCCI vocabulary that CMS retired when it folded that edit table into the PTP table in 2011, and treating a 236 as automatically un-bypassable is a habit left over from that era. Check the pair's modifier indicator.

NCCI edits apply to ASC claims and update quarterly, so a pair that was separately billable last quarter may not be this quarter. Run claims through NCCI logic in the clearinghouse before submission. When procedures genuinely were distinct, modifier 59 or an X modifier can override an edit with indicator 1, but only when the operative note documents the distinction.

Practices that hold up

1. Pre-scheduling eligibility check. Verify the primary CPT code against the current ASC CPL and confirm it is not on the IPO list, before the case is confirmed.
2. Implant charge master review at every quarterly release. One named person, comparing last quarter to this quarter, updating C-codes both directions.
3. Operative note review against billed codes before submission. For multi-procedure cases, compare what the note describes to what is being billed. Procedures billed but not documented are an audit target. Procedures documented but not billed are revenue you already earned and did not capture. A ten-minute charge review catches both.
4. Per-payer authorization matrix, reviewed at contract renewal. Accessible to scheduling staff rather than held in someone's memory.
5. Weekly remittance variance check on multi-procedure cases. Compare expected payment after the reduction against actual payment. Commercial payers not applying contracted ASC rates is common and invisible without this check, and disputes have to be raised inside the contract's timely dispute window. Build the device-intensive caveat above into this report before you run it.

Frequently asked questions

What claim form does an ASC use for Medicare?

The ASC X12 837 professional format, or the CMS-1500 in rare cases. Not the UB-04 or 837I. Some commercial payers want institutional formats, so confirm per contract.

What place of service code should an ASC use?

POS 24 on every line of a standard ASC claim. POS 22 is on-campus hospital outpatient. A wrong POS produces an edit or denial and incorrect patient cost-sharing; it does not get you hospital outpatient rates, because payment follows your enrollment rather than the POS code.

How does the multiple procedure reduction work?

100% of the highest-paying procedure, 50% of the applicable rate for each additional procedure in the same session, on the facility fee. The surgeon's professional fee has its own separate reduction. Adjustments report as CARC 59. Verify the treatment of device-intensive procedures before applying a flat 50% in a variance model.

What is the difference between a pass-through and a packaged implant?

Pass-through devices have a temporary C-code and are separately payable above the bundled rate for at least two but not more than three years. Packaged devices are included in the procedure payment and denied as CARC 96 if billed separately.

How many procedures were added to the ASC CPL for CY 2026?

560. The CMS fact sheet reports 289 added to the CPL plus 271 added as a consequence of removal from the inpatient-only list. This is the largest single-year expansion since the revised ASC payment system launched in 2008.

Is modifier SG still required?

Not for Medicare, since January 1, 2008. Some commercial payers still require it. Verify at credentialing and contract renewal.

What is a device-intensive procedure?

One whose device offset exceeds 30% of the procedure's mean cost, calculated by CMS from claims data at the HCPCS code level. The device HCPCS code must appear on the claim.

What happens if an inpatient-only procedure is performed at an ASC?

Medicare will not pay the ASC facility fee and the claim denies. Note that the IPO list is in a three-year phase-out that began with 285 procedures removed for CY 2026 and is scheduled to finish in CY 2028, so its contents change annually. Coming off the IPO list does not automatically put a procedure on the ASC CPL. Check both lists separately before scheduling.

How we work on this at ROI

ASC denials repeat because the underlying rule gap repeats. The same mismatches produce the same codes month after month until someone changes the process rather than working the claim.

• The platform ingests 835 files from any clearinghouse or PM export and maps ASC CARC and RARC combinations to categories built around the facility fee payment structure rather than generic medical billing buckets.
• Multiple procedure variances are flagged when billed amounts for secondary procedures do not reflect the reduction, which surfaces both compliance risk and commercial payer underpayment in one place.
• Pass-through device denials carry implant classification flags, so the charge master team sees the specific C-code problem instead of a generic non-covered bucket.
• The EDI Code Intelligence Lab carries every CARC and RARC common in ASC billing with ASC-specific fix and prevention guidance.
• The appeal template library covers the denial families ASC claims land in: non-covered service for covered procedure list disputes, coding and billing error for implant classification, and plan provision for place-of-service mismatches. Each letter argues the family and names the documentation that settles it; you supply the procedure and the payer.

If you want to know which mismatches are actually driving your volume before deciding whether any of that helps, the revenue health assessment is free.

"ASC facility billing has tighter rules and less room for interpretation than most other settings. That makes it more learnable, not harder. Once your team understands the covered procedures list, the implant logic, and the multiple procedure rule, most of the denial volume goes away on its own."

Mindy Corbett, CSPO, CPC, CPB, CPPM, Founder, Revenue Optimization & Intelligence

Two things to check in your own center this week

1. Re-run your procedure mix against the CY 2026 CPL. With 560 additions, there is a real chance something you currently send out is now billable in your own building.
2. Confirm your variance report handles device-intensive procedures before it flags a batch of correctly-paid claims as underpayments.

If either turns up something that does not match what is here, tell me. I would rather fix the guide than have the next person work from the wrong number.

Sources

1. Centers for Medicare & Medicaid Services. CY 2026 OPPS and ASC Final Rule Fact Sheet (CMS-1834-FC), November 21, 2025. https://www.cms.gov/newsroom/fact-sheets/calendar-year-2026-hospital-outpatient-prospective-payment-system-opps-ambulatory-surgical-center
2. Federal Register. Medicare Program: Hospital Outpatient Prospective Payment and Ambulatory Surgical Center Payment Systems, CY 2026 Final Rule (published November 25, 2025). https://www.federalregister.gov/documents/2025/11/25/2025-20907/medicare-program-hospital-outpatient-prospective-payment-and-ambulatory-surgical-center-payment
3. Centers for Medicare & Medicaid Services. Medicare Claims Processing Manual, Pub. 100-04, Chapter 14 (Ambulatory Surgical Centers). https://www.cms.gov/regulations-and-guidance/guidance/manuals/downloads/clm104c14.pdf
4. Centers for Medicare & Medicaid Services. ASC Payment System: approved HCPCS codes, payment rates, and covered procedures. https://www.cms.gov/medicare/payment/prospective-payment-systems/ambulatory-surgical-center-asc
5. Centers for Medicare & Medicaid Services. ASC Payment Rates Addenda. https://www.cms.gov/medicare/payment/prospective-payment-systems/ambulatory-surgical-center-asc/asc-payment-rates-addenda
6. Centers for Medicare & Medicaid Services. MM14359, ASC Payment System January 2026 Update. https://www.cms.gov/files/document/mm14359-ambulatory-surgical-center-payment-january-2026-update.pdf
7. eCFR. 42 CFR 419.66, Transitional pass-through payments for medical devices. https://www.ecfr.gov/current/title-42/chapter-IV/subchapter-B/part-419/subpart-G/section-419.66
8. eCFR. 42 CFR 416.166, ASC covered surgical procedures. https://www.ecfr.gov/current/title-42/chapter-IV/subchapter-B/part-416/subpart-F/section-416.166
9. Centers for Medicare & Medicaid Services. Prior Authorization Demonstration for Certain Ambulatory Surgical Center Services. https://www.cms.gov/data-research/monitoring-programs/medicare-fee-service-compliance-programs/prior-authorization-pre-claim-review-initiatives/prior-authorization-demonstration-certain-ambulatory-surgical-center-services
10. Centers for Medicare & Medicaid Services. Place of Service code set (Transmittal R3873CP). https://www.cms.gov/regulations-and-guidance/guidance/transmittals/2017downloads/r3873cp.pdf
11. Medicare Payment Advisory Commission. Report to the Congress, ambulatory surgical center services chapter (March 2025). https://www.medpac.gov/wp-content/uploads/2025/03/Mar25_Ch10_MedPAC_Report_To_Congress_SEC.pdf
12. Ambulatory Surgery Center Association. CMS Releases 2026 Final Payment Rule. https://www.ascassociation.org/asca/news-and-publications/news/2025/2026-final-payment-rule
13. X12.org. Claim Adjustment Reason Codes. https://x12.org/codes/claim-adjustment-reason-codes