Cardiff City have been told by the FIFA Players' Status Committee to pay Nantes €6 million for the late Emiliano Sala.
The striker became Cardiff's record signing when a deal was struck with the Ligue 1 club in January.
But before he made an appearance for City, the plane carrying Sala from France to Wales crashed and he was killed, along with pilot David Ibbotson.
Cardiff claimed the agreement to pay Nantes a £15million fee was not legally binding because conditions insisted upon by Nantes were not fulfilled.