The database on transnational cases involving the erosion of the taxable base showcases abusive cross-border tax planning structures and respective risk indicators mostly in developing countries. This service describes transnational cases of intentional tax base erosion, based on real cases and prepared according to a standard that facilitates their analysis. It includes general information on the taxation systems of 24 Centro Interamericano de Administraciones Tributarias (CIAT) member countries from the Americas, Europe and Africa that is necessary to analyse, compare and interpret the 34 cases reported by 18 countries, mainly in 2019, which involve aggressive tax behaviours. Its objective is to provide the tax administrations with information for identifying aggressive tax behaviours by businesses and/or individuals who carry out international transactions and their respective characteristics, for the ultimate purpose of generating cooperation that may result in coordinated actions. The system allows the cases to be filtered by country, taxpayer behaviour and economic sector.