Atalanta will not activate the option to buy Mattia Caldara, who returns to Milan.
The Rossoneri sent Caldara back to his former club on loan with an option to buy in January 2020, but the centre-back has struggled after returning to Bergamo.
The 27-year-old will return to Milan, where he has a contract until June 2023 after only six Serie A appearances in 2020-21 with La Dea.
Atalanta sold Caldara to Juventus for €19m in January 2017, when he immediately returned on loan to the Nerazzurri.
He then moved to Milan from Juventus in August 2018, when Leonardo Bonucci moved in the opposite direction.
Milan had been hoping to pocket €15m for the defender, but La Dea have no intentions of making the move permanent after only nine competitive appearances.