Butler will enter restricted free agency after reportedly turning down a four-year, $40 million offer from the Bulls in October.
As a restricted free agent, Butler will be able to sign an offer sheet with any team, but Chicago has the right of first refusal and can match any offer.
In January, the Chicago Tribune reported that the Bulls expect to sign Butler to a maximum contract.
Outside of Chicago, teams are already preparing possible maximum-salary offer sheets for Butler in free agency, including the Los Angeles Lakers as one of several expected suitors, league sources told RealGM.
Butler, who is 25 years old, is wrapping up a breakout season.
Over 65 games, he averaged 20.0 points, 5.8 rebounds and 3.3 assists while shooting 46.2 percent from the field and 37.8 percent from three-point range.
Butler earned his first All-Star nod and was named the NBA's Most Improved Player.