The booklet describes interoperability system 'Trembita' for secure data exchange between government registers and databases of Ukraine. The 'Trembita system' improves public service provision and makes the governance more transparent and effective in Ukraine. 'Trembita system' is developed by Cybernetica (Estonia) and Soft Expansion (Ukraine) and implemented within EGOV4UKRAINE project of U-LEAD programme in 2017 - 2020. The development and implementation is financed by EU and its member states Denmark, Estonia, Germany, Poland and Sweden.