Abstract Introduction: Despite being preventable, tooth decay is the most common oral disease affecting a quarter of 5-year-olds children in England (2016). Stark inequalities exist ranging from 4% to 56% of 5-year-olds having decay at a local authority level. Poor oral health can affect children's ability to sleep, eat, speak, play and socialize and was the most common reason for hospital admission for children aged 0-18 years (2014-15).Methods: PHE commissioned York Health Economics Consortium to develop a return on investment (ROI) tool for oral health improvement programmes in young children to support local authority investment decisions. The ROI tool has been developed with reference to the best available evidence and used cost effectiveness data of oral health interventions and estimates the economic benefits of oral health programmes to reduce dental decay in 5 year old children. The programmes included in the ROI tool are: supervised tooth brushing, fluoride varnish, provision of toothbrushes and paste by post, health visitors and water fluoridation.Results: The ROI tool provides information on monetised saving to the local authority from the reduction in days missing off work for parents/carers and the savings to the NHS from the reduction in the treatment of tooth decay.Conclusions: This well received ROI tool has assisted local authorities in their commissioning decisions providing an estimate of the return on investment of the programmes included, using the oral health profile of their local population. The ROI tool also helps to estimate the impact on oral health inequalities. External funding details N/A