Billing Basics for Ambulatory Surgery Centers

An Ambulatory Surgical Center (ASC) is defined by CMS as a facility with the sole purpose of providing outpatient surgical services to patients. Ambulatory surgical centers can be identified with a hospital-based entity or can be a freestanding outpatient surgical center. 

While ASC claims have some similarities to hospital claims when it comes to billing, there are some very distinct differences.

Which ASC Billing Claim Forms to Use

Woman sitting on a hospital bed in the hallway


Ambulatory surgical center claims are filed to Medicare, Medicare Advantage Plans, and Medicaid on an HCFA 1500 or the 837P. This is different from hospital outpatient surgery claims to the payers, which are filed on the UB-04 or the 837I.

The CMS-1500 is the red-ink on white paper standard claim form used by physicians and suppliers for claim billing. Any non-institutional provider and supplier can use the CMS-1500 for billing medical claims. The electronic version of the CMS-1500 is called the 837-P, the P standing for the professional format.

The UB-04 or 837-I is used by ASCs to file medical claims to all other payers.

Bill Type for ASC

When submitting claims on the UB-04, the bill type for ASC claims is 83X.The first digit refers to the type of facility: 8 - Specialty Facility, Hospital ASC Surgery The second digit refers to the bill classification: 3 - Outpatient

The third digit refers to the frequency which is represented above by the variable X.

1 - Admit Through Discharge Claim

7 - Replacement of Prior Claim or Corrected Claim

8 - Void or Cancel of a Prior Claim

Revenue Code

When submitting claims on a UB-04, the revenue code used to report ambulatory surgical center procedures is 490.

The Use of Modifiers

ASC claims can be somewhat confusing because different payers not only require different types of claim forms, they also require the use of different modifiers.

Medicare Modifiers

Medicare requires the following modifiers when filing certain procedure codes for ASC claims:

Modifier RT - Right side (used to identify procedures performed on the right side of the body)

Modifier LT - Left side (used to identify procedures performed on the left side of the body)

Modifier TC- Technical component

Modifier 52 - Reduced services

Modifier 59 - Distinct separate procedure

Modifier 73 - Procedure discontinued after prep for surgery

Modifier 74 - Procedure discontinued after anesthesia administered

Modifier FB - Device furnished at no cost/full credit

Modifier FC - Device furnished at partial credit

Modifier PA - Wrong body part

Modifier PB - Surgery wrong patient

Modifier PC - Wrong surgery on patient

Modifier PT - Colorectal screening converted to diagnostic or therapeutic procedure/surgery

Modifier GW - Surgery not related to hospice patients terminal condition

Medicaid Modifier

Even though Medicare uses these modifiers, Medicaid does not require the use of any of these. The only valid modifier for Medicaid is modifier SG which distinguishes the claim as an ambulatory surgical center claim.

It is necessary to append modifier SG to every CPT code regardless of the payer in order to distinguish the billing from the professional claim for the same service.

Other Insurer Modifiers

Another example of a difference in the use of modifiers is that Blue Cross Blue Shield** requires the use of modifier 50, which distinguishes the procedure as a bilateral procedure, with 2 units of service. Medicare, on the other hand, requires either a modifier 50 or modifier RT and LT on separate lines with 1 unit of service.

**Billing guidelines may vary by state. Check with the BCBS state manual to find out.

Was this page helpful?