The 26-year-old spent last season on loan at Vitesse Arnhem after struggling to make an impact in Germany, and Schalke general manager Horst Heldt has confirmed that an offer has been made.
"There has been a concrete offer submitted. It is a good option for Tony and we have accepted. This offer will now be discussed by Anthony Annan and his agent," Heldt told Westdeutsche Allgemeine Zeitung.
Annan has been linked with a move to Osasuna.