Modifier 73 identifies a surgical or diagnostic procedure discontinued at an Ambulatory Surgery Center (ASC) or outpatient hospital prior to anesthesia administration due to extenuating circumstances or a threat to patient well-being, entitling the facility to 50% of the applicable fee schedule allowable.
When a patient is prepped, transported to the OR, and the case is called off before anesthesia begins, the facility has already consumed real resources, including staff time, pre-operative preparation, sterile equipment, and OR scheduling. Modifier 73 helps facilities recover part of the resources already used before cancellation, but Modifier 73 ASC and outpatient claims remain among the most frequently misapplied facility claims.
According to the CMS Medicare Claims Processing Manual, this Modifier governs pre-anesthesia discontinuation, while Modifier 74 applies once anesthesia begins. Using the wrong Modifier can lead to denials, audits, and repayment requests. ASC Billing Services are built to manage these distinctions so your facility does not leave reimbursement on the table.
What Is Modifier 73 in Medical Billing?
The official Modifier 73 description, as defined by CMS and CPT, is “Discontinued Outpatient Hospital/Ambulatory Surgery Center (ASC) Procedure Prior to the Administration of Anesthesia.” It signals that a procedure was fully prepared and scheduled but canceled before the patient received any form of anesthesia.
CPT Modifier 73 is facility-only and applies exclusively to outpatient hospital and ASC claims. In similar cases, the physician would use Modifier 53. Physician claims generally cannot use Modifier 73 and will often be denied automatically if it is appended.
When to Use Modifier 73?
For Modifier 73 reimbursement to apply, facilities generally need to meet three conditions. Modifier 73 only applies when the procedure is stopped for a medical or patient safety reason, not because of scheduling or administrative issues. The following clinical circumstances may qualify as acceptable clinical triggers: acute hypertension identified in pre-op, positive pregnancy test, unexpected contraindication to the surgical procedure, or an allergic reaction to a pre-op medication.
Modifier 73 only applies to outpatient hospitals and ASCs. Elective cancellations generally do not qualify for Modifier 73 reimbursement.
How Anesthesia Is Defined Under Modifier 73
Anesthesia is often defined in a much broader scope than what many billers expect, especially by CMS. Anesthesia, from a CMS or payer point of view, includes both local and regional nerve blocks, moderate and deep sedation, as well as general anesthesia. Routine medications given pre-operatively are typically not considered an anesthetic unless they are intended to induce sedation.
Once a service has been provided that includes anesthesia, then the procedure/service no longer qualifies for Modifier 73 and instead will require Modifier 74 to be attached on the claim for the facility to receive appropriate payment for the service performed. Accurate pre-operative documentation will support the use of the appropriate discontinued Modifiers.
Medicare vs. Commercial Payer Reimbursement: What Billers Need to Know
Modifier 73 is used by Medicare to reimburse 50% of the ASC or outpatient facility allowable for claims billed under the ASC payment rules as outlined in Chapter 4 of the CMS Medicare Claims Processing Manual. The reimbursement methodology applies to all standard Medicare Part B fee-for-service (FFS) claims.
However, commercial payers tend to have less consistency in their reimbursement policies and procedures for Modifiers. For example, each of the following insurers may apply a different reimbursement policy for procedures that have been discontinued (UnitedHealthcare, Aetna, and Blue Cross/Blue Shield); therefore, if one insurer applies a lower reimbursement percentage, requires additional documentation, or restricts use of Modifier 73 to certain procedure types, then the other insurers may also do the same.
Reimbursement from Medicare Advantage plans frequently will differ from traditional Medicare reimbursement due to the fact that the reimbursement provisions of the plans are set by the individual plan contracts rather than solely by the provisions contained within traditional Medicare.
Prior to submitting a claim for a Modifier 73, a biller should review the payer’s discontinued procedure policy and any applicable Local Coverage Determination (LCD); if the MAC jurisdiction does not have an LCD, then both the National Coverage Determination (NCD) and the payer’s provider manual should be reviewed in order to verify specific billing requirements and eligibility for reimbursement.
Modifier 73 Usage Guidelines (Do’s and Don’ts)
Do’s
- Apply Modifier 73 only on the primary planned CPT code.
- In most cases, use Modifier 73 on only one CPT code per date of service.
- It is important to verify that the procedure was stopped prior to administering anesthesia and before starting the procedure.
- A thorough review of EHR and pre-operative documentation should be done regularly to ensure coding accuracy.
- Use Modifier 52 instead when a procedure is reduced, and anesthesia was not planned.
Don’ts
- Do not rely on carry-forward notes in an EHR that are not accurate. These can create incorrect coding and billing.
- Do not report Modifier 73 on secondary CPT codes, as this may trigger bundling edits and NCCI conflicts that can lead to claim denials.
- Do not use modifier 73 for elective cancellations.
- Do not report modifier 73 on physician Claims. Modifier 73 is only for facility use.
- Do not use modifier 73 for procedures done inpatient.
- Do not confuse modifier 73 and modifier 74. Modifier 74 signifies that anesthesia was administered before the procedure began.
Real-World Examples of Modifier 73
The following Modifier 73 examples illustrate how clinical documentation supports each discontinued procedure claim.
Discontinued Inguinal Hernia Repair (CPT 49520)
An ASC patient was scheduled to have surgery to repair a recurrent inguinal hernia. The patient had completed the preoperative preparation and was in the procedure room when the anesthesiologist recorded the patient’s blood pressure, which was 210/120.Â
The surgeon canceled the inguinal hernia repair due to the patient’s elevated blood pressure, and no anesthetic had been administered. The ASC bills CPT 49520 with Modifier 73, using the documented blood pressure findings to support the discontinued procedure claim.
Pelvic Fracture Surgery Canceled Due to Pregnancy
A patient was scheduled for an open reduction of a pelvic fracture and completed routine preoperative labs. The patient tested positive for pregnancy after being taken to the procedure room but before induction of anesthesia. The surgeon canceled the pelvic fracture procedure immediately, and the facility billed CPT 27216 (percutaneous skeletal fixation of pelvic ring fracture) with Modifier 73.
Cystourethroscopy Canceled Pre-Anesthesia
In case of a patient who has a routine diagnostic cystourethroscopy, an allergy to a preoperative antibiotic administered in the holding area before becoming unconscious causes the procedure to be canceled. The ASC bills to the CPT code with Modifier 73, with the allergic reaction documented in the nursing pre-op notes to document the medical necessity for the cancellation.
Colonoscopy Aborted Before Sedation
A patient presents for a routine screening colonoscopy and has chest pains prior to being sedated. The procedure is halted before any sedation is administered, and the patient is transported to the emergency room. Because no sedation had been administered before cancellation, the case still qualifies for Modifier 73. The medical record indicates that there was a cardiac event leading to this cancellation.
How to Bill Modifier 73 Correctly
Step 1: Verify the claim came from an ASC or outpatient facility and not from an inpatient facility or a physician professional claim.
Step 2: Check the pre-anesthesia and/or nursing notes before the cancellation to ensure that no anesthesia was given prior to cancellation.
Step 3: Make sure the medical record clearly explains why the cancellation was medically necessary.
Step 4: Report the Modifier only on the originally planned CPT code for services; limit to one code per date of service.
Step 5: Submit the claim on the UB-04 (CMS-1450), entering Modifier 73 in Form Locator 44. For electronic submission, file the 837I transaction, not the 837P, which is reserved for physician claims.
Step 6: Review each discontinued procedure modifier claim against current NCCI edits before submission to catch coding conflicts early.
Step 7: Review the ERA (Electronic Remittance Advice) & 835 transaction following submission; confirm payment at half of the allowable amount; analyze CARC (Claim Adjustment Reason Codes) or RARC (Remittance Advice Remark Codes) on complete denials to determine if they can be corrected, resubmitted, or if an appeal should be initiated.
Frequent Modifier 73 denials often point to workflow or documentation gaps that need review. Access Nexus io’s Denial Management Services to proactively prevent write-offs before submission.
Modifier 73 vs Other Discontinued Procedure Modifiers
| Modifier | When to Use | Common Mistake | Denial Risk |
| Modifier 73 | Outpatient/ASC, discontinued before anesthesia, facility only | Applying to physician claims or after anesthesia has started | High |
| Modifier 74 | Outpatient/ASC, discontinued after anesthesia, pays at 100% | Using when anesthesia was never given | Moderate |
| Modifier 52 | Reduced service with no planned anesthesia, facility, or physician | Using when anesthesia was planned but not given | Moderate |
| Modifier 53 | Discontinued by the physician after anesthesia, professional claims only | Applying to ASC or facility claims | High |
Practices to Avoid Modifier 73 Denials
Modifier 73 and other related modifiers for discontinued procedures continue to rank within the top sources of ASC facility claims denied. The Kodiak Solutions 2024 Revenue Cycle Benchmarks Report shows that initial denial rates in ambulatory settings are a significant cost driver and that using modifier-specific documentation and scrubbing protocols represents one of the best means for directly protecting Revenue.
Denial management reports generated each month by Modifier type and payer will allow staff to identify trends/flags as early as possible. Each quarter, an audit of the EHR template carry-forward documentation should be conducted to ensure that inaccuracies in pre-op records do not lead to claim denials. Nexus io’s Medical Coding Services and structured revenue cycle management (RCM) workflows address each of these exposure points systematically.
Conclusion
Modifier 73 in medical billing carries strict rules that must be adhered to, which include that it can only be used for facility claims, it can only be used for pre-anesthesia claims, only one CPT code can be submitted for each DOS, and there must be clinical justification for each use of the Modifier.
When used correctly with appropriate documentation, Modifier 73 allows recovery of legitimate facility expenses and can withstand audit by RAC and OIG. There are many points of failure in using Modifier 73, including elective cancellations, wrong Modifier appending, and gaps in documentation, that can all be avoided with instruction on how to use Modifier 73, scrubbing claims to ensure no administrative errors, and coordinating clinical and billing activities for efficiency.
Nexus io’s Healthcare Revenue Cycle Management team helps ASCs and outpatient facilities reduce Modifier denials and recover revenue faster. Contact us today to audit your Modifier workflows and stop leaving reimbursement on the table.
Frequently Asked Questions
What is Modifier 73 in medical billing?
Modifier 73 is a facility-only modifier used on outpatient hospital and ASC claims when a patient has been prepped and brought to the procedure area, but the procedure is canceled before anesthesia is administered due to extenuating circumstances or a threat to patient safety. The facility is reimbursed at 50% of the fee schedule allowable.
When should you append Modifier 73?
When a patient was prepped and taken to the procedure area, the procedure was canceled due to clinical necessity before any anesthesia was given, and the claim is a facility claim limited to one CPT code per DOS.
What causes a Modifier 73 denial?
Common causes include: reporting elective cancellations, applying the modifier to physician claims, submitting multiple CPT codes per date of service, missing clinical justification in the medical record, and confusing Modifier 73 with Modifier 74 or Modifier 52.
How does Modifier 73 differ from Modifier 74?
Modifier 73 is reimbursement at 50% for pre-anesthesia, and Modifier 74 is 100% reimbursement for post-anesthesia or after incision. Both Modifiers are for facility-only claims, so they cannot be included on Physician claims.
Can a Modifier 73 denial be appealed?
Yes, you must submit preoperative nursing documentation, as well as the ordering Physician’s cancellation order and supporting clinical documentation, such as laboratory or vital sign results to the payer within 30 to 120 days after the appeal process begins, depending on the type of plan you have.
How do you prevent Modifier 73 claim scrubbing failures?
The next step to successfully filing this claim is to load your current NCCI and payer-specific policies into your claim scrubbing tool. All claims for discontinued procedures should be flagged for a secondary review prior to filing your claim, and you should audit EHR templates at least once every three months to minimize errors related to carry-forward documenting.
