The IDI (Enterprise Identification Number, UID in German) is a unique code assigned to every registered enterprise in Switzerland by the Federal Statistical Office (FSO). Format: CHE-XXX.XXX.XXX (9 digits with CHE prefix). Every active enterprise in Switzerland has one. It is used for: 1) Unique identification across all federal, cantonal and municipal authorities; 2) Simplifying administrative procedures (single number for VAT, AVS, commercial register, customs); 3) The Swiss VAT number is the IDI followed by 'MWST'/'TVA'/'IVA'. Verification is free at www.uid.admin.ch. Foreign enterprises operating in Switzerland also receive an IDI.