ResCare will announce today that it needs more time to review private-equity firm Onex’s $12.60-a-share offer for the stake it doesn’t already own, a source close to the situation said.

The Toronto-based private-equity firm has a 24.9 percent voting stake in ResCare, which provides job training and education support to individuals with developmental or other disabilities. There was a deadline of today for ResCare to make a recommendation.

Onex’s offer, which values the company at roughly $300 million, is more complex than it appears, the source said.

ResCare’s shares closed Wednesday at $12.42 a share.