This document provides guidance on the scope of the Psychological Therapies and Interventions Waiting Times Standard for staff that are employed by Health Boards (NHS) and who deliver psychological therapies and interventions through Health and Social Care Partnerships (H&SCP) and hospitals. The Standard states that 90% of people should start psychological treatment or intervention within 18 weeks of referral. This document sets out what constitutes psychological therapies and interventions (by services, teams, individuals, or digitally), defines the clock start and clock stop times and specifies how the waiting time from referral to treatment start (RTT) is to be calculated and reported to Public Health Scotland for publication.