A Kings spokesman confirmed Wednesday night that the move was made several weeks ago after Voynov was injured outside normal hockey training.
The move means Voynov's contract doesn't count against Los Angeles' salary cap. The two-time Stanley Cup champion would carry a $4.166 million cap hit for four more seasons for the Kings, who need all the cap room they can get with several players signed to lucrative long-term contracts.
The Russian defenseman tore his right Achilles tendon earlier this year and had surgery in March. The Kings were able to suspend him because the injury wasn't related to hockey workouts, although it's not clear exactly how he was hurt.
His Kings suspension lasts until he is physically able to play again, and the club isn't sure when he'll be healthy.
Voynov hasn't played since he was arrested in October and eventually charged with felony domestic violence against his wife. The Kings finished the season without their No. 2 defenseman, and the defending Stanley Cup champions missed the playoffs.
Voynov is scheduled to stand trial July 6 on the felony charge after several delays.
The NHL allowed the Kings to take his contract off their salary-cap commitments last season, but the new suspension gives them some financial flexibility heading into the free-agent signing period.
The move was first reported by the Kings' official website.