There is increasing interest and belief in applying quality improvement (QI) to help solve our most complex challenges in healthcare, yet little published literature to help leaders develop a business case and evaluate return on investment from QI. This is even more pronounced in fields such as mental health and community health services. This paper from Amar Shah and Steven Course presents a framework to help identify, understand and evaluate return on investment from large-scale application of QI in healthcare providers. The framework has been developed at East London NHS Foundation Trust (ELFT), a provider of predominantly mental health and community health services to a population of 1.5 million people, which has been undertaking QI at scale since 2014. This paper presents case studies and examples from ELFT to illustrate return on investment from QI at multiple levels: improving outcomes for patients and service users, improving the experience of staff, improving productivity and efficiency, avoiding costs, reducing costs and increasing revenue.