Modifier 53 (Discontinued Procedure) signals that a surgical or diagnostic service was begun by the physician but terminated because of extenuating circumstances that threatened the patient’s well‑being. The AMA CPT® definition specifies this applies when a procedure is started (for example, anesthesia given and incision or scope insertion performed) and then discontinued due to events such as adverse anesthesia reaction, airway obstruction, cardiac arrest, hemorrhage, or hemodynamic instability. It must not be used for elective cancellations before anesthesia or surgical preparation; facility modifiers –73 or –74 apply in those situations.

This modifier is intended for provider (physician) professional services only and must be appended in the pricing (primary) position on the claim line. Adequate documentation is required: note that the procedure was started, explain why it was discontinued (medical risk/extenuating circumstance), and, when possible, state the percentage or extent of the service completed. Facility claims use the facility‑level modifiers (–73/–74) rather than -53.

Modifier 53 affects payment. Medicare typically pays proportionally to the percent of the service actually completed (for example, reimbursing 60% if roughly 60% of the procedure was performed). Some commercial payers apply a flat reduced payment (commonly cited as 25% of the allowable charge), although payers may make exceptions for specific code–modifier combinations where unique RVUs or rules apply. Always document clinical rationale clearly to support the discontinued‑procedure billing.