Ambulatory Surgery Center (ASC) Billing Services

An ambulatory surgery center bills the facility side of an operation. The surgeon bills separately for professional work, and the anesthesia group bills on its own. ASC billing covers the center's fee for the room, nursing, supplies, and many devices.

ASC medical billing has its own rules. Medicare pays only for procedures on its covered list, applies reductions when several procedures are done, and handles implants in particular ways. Commercial contracts often differ from Medicare. Westmont connects ASC owners and administrators with vetted billing experts who understand facility claims, case costing, and payer contracts across many specialties.

Who this is for

• Single-specialty and multi-specialty ASCs
• Physician-owned and hospital-affiliated centers
• ASC administrators and business office managers
• Surgeons who own or invest in a center
• Centers adding new service lines, such as spine or cardiology
• Centers changing billing vendors

What gets billed

• Facility fees for outpatient surgery
• Colonoscopy and upper endoscopy
• Cataract surgery
• Orthopedic and sports medicine procedures
• Pain management injections
• Gallbladder and hernia surgery
• ENT and urology procedures
• Implants and devices that are separately payable
• Drugs and supplies, when allowed
• Facility charges for procedures that end early

Commonly billed codes

Code	Type	What it covers
45378	CPT	Diagnostic colonoscopy
45385	CPT	Colonoscopy with polyp removal by snare
43239	CPT	Upper scope with biopsy
66984	CPT	Cataract removal with lens implant
29881	CPT	Knee scope with meniscus work
64483	CPT	Lower back transforaminal epidural injection, single level, with imaging
47562	CPT	Laparoscopic gallbladder removal
G0105	HCPCS	Colon cancer screening for high-risk patients
24	Place of service	Ambulatory surgical center
73	Modifier	Procedure stopped before anesthesia
74	Modifier	Procedure stopped after anesthesia began
Z12.11	ICD-10-CM	Screening for colon cancer

Note

Codes are examples for orientation, not a complete list, and do not guarantee coverage or payment. Always check current code sets and payer policy.

Billing challenges in ASC billing

• Covered procedure list. Medicare pays an ASC only for procedures on its covered list, which CMS updates each year. A biller experienced in ASCs checks the current list before a new case type is scheduled.
• Multiple procedures. Medicare generally reduces payment for additional procedures in one session. Billers order codes correctly so the higher-paid procedure is first and the reductions apply as intended.
• Implants and devices. Some devices are paid separately and some are packaged into the procedure payment. Billers match device codes to invoices and watch payer carve-outs.
• Screening to diagnostic conversions. A screening colonoscopy that turns diagnostic changes coding and patient cost sharing. Billers use the correct codes and modifiers, such as PT, and explain the change to the patient.
• Canceled procedures. Modifiers 73 and 74 show a procedure stopped before or after anesthesia began, and they affect payment. Billers review notes for the right modifier.
• Prior authorization and benefits. Commercial payers vary on what they approve for a facility. Billers verify authorization for the facility as well as the surgeon.
• Contract and underpayment review. Commercial rates may be set as a percent of Medicare or by case. Billers compare payments to contracts and flag shortfalls.
• Quality reporting. Medicare ASCs participate in a quality reporting program, and missing it can reduce updates. Billing partners should support accurate data.

How Westmont can help

• Matching you with vetted billing experts experienced in ASC facility billing
• End-to-end revenue cycle support, from verification to payment posting
• Denial management and underpayment review against payer contracts
• Credentialing and enrollment support for new centers and added specialties
• Reporting by surgeon, specialty, and payer to help you manage the center

Frequently asked questions

What is the difference between ASC billing and physician billing?

ASC billing covers the facility: the room, staff, supplies, and equipment. Physician billing covers the surgeon's professional work, and anesthesia bills separately. The ASC uses a facility claim form and its own payment rules. Both sides must report matching procedure codes.

Which procedures will Medicare pay an ASC to perform?

Medicare pays only for procedures on its ASC covered procedures list. CMS updates the list each year through its payment rule. Check the current year's list before adding a new service, and confirm commercial payers' rules too. Commercial payers may follow their own lists, which can differ from Medicare's.

How does Medicare treat multiple procedures at an ASC?

Medicare generally pays the full rate for the highest-paying procedure and a reduced rate for others in the same session. Not every code qualifies. Billers sequence codes carefully and review how each payer applies the reduction. The reduction rules can also differ for commercial payers, so contract terms should be reviewed.

Why are ASC claims denied?

Typical causes are missing authorization, a procedure not on the covered list, mismatched codes between facility and surgeon, and missing device information. A pre-claim review catches many of these. Facility and surgeon coding should match, and implant invoices should be saved for any payer audit.

Can an ASC outsource its billing?

Yes. Many centers do, particularly when they add specialties. Look for a partner that understands facility claims, implants, contracts, and denial follow-up, and ask how it reports results to administrators. It should also be able to review contracts, track underpayments, and give administrators clear, regular reports.

Related billing services

• Surgical Hospitals
• Anesthesiology
• Orthopedic Surgery
• Gastroenterology
• Ophthalmology
• Pain Management