In case your trip is fully sponsored by a third party in Germany (friend, relative or organization), the host will need to send you a formal letter of obligation (“Verpflichtungserklärung”). This is an official document issued by an Aliens Department (“Ausländerbehörde”) in Germany, stating that the host in Germany will cover all costs incurred by your visit. Alien Departments are the German public authority responsible for foreigners. They are usually located in every administrative district (“Landkreis”), mostly in the town hall of the district town (“Kreisstadt”).