It's officially September, but the trading season isn't necessarily over. Here's what you need to know about dealmaking after August.
Trading in September is a lot like trading in August. Players who have cleared waivers can be traded to any team, but players who have been pulled back from waivers can't be traded. However, to be eligible for postseason play "a player must be on the Active Roster, Disabled List, Bereavement List, or Suspended List of that club as of midnight EDT on August 31 of that year," as Keith Law explains in this ESPN article. Because of that rule, most deals occur before September.
Trades do happen in September, since acquisitions can help teams reach the playoffs. For example, the Phillies famously traded for Sparky Lyle in September of 1980. Lyle was a major contributor for the '80 Phillies team, even though he wasn't able to play in the postseason en route to the team's first World Series title.
A version of this post was originally published in 2009.