This paper describes work undertaken with Age UK Herefordshire and Worcestershire to design a service that addresses loneliness, particularly among older people. The first half of the paper examines the potential costs of loneliness and the potential value to the public sector of reducing loneliness. The second half of the paper describes the outcomes-based model used in Worcestershire and sets out initial findings of the service. The service uses a model of commissioning services through a Social Impact Bond (SIB), a contract in which commissioners commit to pay investors for an improvement in social outcomes. The paper sets out some of the benefits of using social investment to fund the upfront cost of delivering a service to reduce loneliness. It also discusses the following elements of the model: measuring loneliness and additional outcomes, delivering support to the population most at risk, considering social investment and agreeing a payment mechanism.