The Once-Only Principle Project (TOOP) was launched by the European Commission in January 2017 as an initiative of about 51 organisations from 21 EU Member States and Associated Countries. The main objective of TOOP is to explore and demonstrate the once-only principle across borders, focusing on data from businesses. Doing this, TOOP wants to enable better exchange of business-related data or documents with and between public administrations and reduce administrative burden for both businesses and public administrations.