The 8-Minute Rule is a Medicare billing guideline used to determine how many time-based units of therapy services—such as physical therapy, occupational therapy, or speech therapy—a provider can bill for in a single patient session. Under this rule, therapists can bill one unit for any service lasting at least 8 minutes but less than 23 minutes, with additional units added for each subsequent 15-minute increment (e.g., 23–37 minutes = 2 units, 38–52 minutes = 3 units, and so on). The rule applies only to time-based CPT codes, not service-based codes, and is crucial for ensuring compliance with Medicare regulations while avoiding overbilling.