Financial crimes are increasingly sophisticated, with criminals accumulating significant sums through offences such as drug trafficking, fraud, extortion, corruption and tax evasion. Different government agencies may be involved in detecting, investigating and prosecuting these offences and recovering the proceeds of crime, or may hold information essential to these activities. This report describes the current position in 51 countries as to the law and practice for domestic inter-agency co-operation in fighting tax crimes and other financial crimes including, for the first time, co-operation with authorities responsible for the investigation and prosecution of corruption. It identifies successful practices based on countries’ experiences of inter-agency co-operation in practice and makes recommendations for how co-operation may be improved.