The 8-Minute Rule is a Medicare billing guideline used to determine how many units of time-based therapy services can be billed during a patient session. According to this rule, a healthcare provider must deliver at least 8 minutes of a one-on-one, billable service—such as physical therapy, occupational therapy, or speech-language therapy—to bill for one unit. The rule follows a time range structure where, for example, 8–22 minutes equals one unit, 23–37 minutes equals two units, and so on.