The shareholders of Coordinated Auction Office in South East Europe are eight Transmission System Operators from the South East European region:

Croatia HOPS Croatian Transmission System Operator Plc.
Bosnia and
Herzegovina
NOSBiH Nezavisni operator sistema u Bosni i Hercegovini
Montenegro CGES Crnogorski elektroprenosni sistem AD
Albania OST Operatori i Sistemit te Transmetimit
Kosovo KOSTT Operator sistemi, transmisioni dhe tregu Sh.A.
Greece IPTO Independent Power Transmission Operator S.A.
Türkiye TEIAS TÜRKIYE ELEKTRIK ILETIM A.S.
North Macedonia MEPSO Оператор на електропреносниот систем на Република Северна Македонија