Tax administrations across the globe raise hundreds of billions of euros every year in revenue to fund vital public services. Much of this depends on taxpayers complying voluntarily with their obligations, and small positive shifts in this behaviour can lead to significant additional revenue. This report sets out how the use of behavioural insights can influence the behaviour of taxpayers to help deliver those positive shifts. It covers strategic considerations as well as a high-level discussion of the methods employed by behavioural scientists. The report also provides concrete examples of how behavioural insights have been used in tax administration and highlights prospective uses and strategic considerations. Finally, the report sets out some practical guidance for tax administrations considering growing the use of behavioural insights.