The purpose of this study is to collect data on adverse events from third party registries that include information about adverse events from patients with haemophilia B treated with nonacog beta pegol. The third party registries include PedNet Haemophilia Registry (PedNet) and the European Haemophilia Safety Surveillance System (EUHASS). Data from national and international registries in countries where nonacog beta pegol has been approved and marketed could be included in the data collection.