The Bundesliga giant is eager to see the Germany youth international stay at the BayArena this summer but has confirmed that he has a buyout clause.
The young midfielder has spent just one season at the BayArena after moving from Bayern Munich last summer in search of first-team football.
His performances have caught the eye of the Premier League runner up and Voller has confirmed that there is a clause in his contract.
"We know of their interest, but there is nothing official," he told Bild. "Of course Emre has a clause in his contract now. We're still waiting for a decision. [A 12 million euro return on a €5.5 million] investment would be lucrative business. But that is not the sticking point. We are of the opinion that Emre would do well with another year with us. Roger Schmidt has already spoken to him, he is really into the player.
"I am convinced that Can would be even better with Roger."
Bayern has a buy-back clause with Emre and Voller says the Bavarians want the player to spend another year in the Bundesliga before returning.
"Of course I spoke with Karl-Heinz Rummenigge on the subject. Bayern think that another season at Leverkusen would be right for Emre."