The Happier, Healthier Professionals research programme aims to support the profession by understanding how local authorities might address rates of employee sickness absence and turnover by introducing interventions designed to alleviate stress and increase employee wellbeing. In this trial, we will test whether providing social workers with a letter of gratitude for their hard work and efforts, incorporating two lines of positive feedback from their team manager, and coming directly from a senior-level figure in their local authority (e.g. Director for Children’s Services), will boost social worker wellbeing and subsequently reduce sickness absence rates. We hypothesise that social workers who receive a letter will subsequently experience an increased sense of feeling valued and recognised by their local authority, an increased sense of belonging to their workplace, a boost in their motivation, and an increased sense that their work positively impacts others. The letters will be randomly allocated to individual social workers across 4 local authorities and its impact will be measured over 3 months, between September and November 2019.