Trade Assignment Waivers
The deadline for "non-waiver" (unrestricted) trades is 4 PM (EDT) on July 31st. Beginning on August 1st and extending through to the conclusion of the MLB regular season, Trade Assignment Waivers must be secured before players on MLB 40-man rosters can be traded. (Waivers are never required to trade players on minor league reserve lists).
If a player is placed on Trade Waivers and is not claimed, waivers are said to be "secured" and the player can be traded to any MLB club at any time, just like prior to the non-waiver trade deadline.
Trade Assignment Waivers are revocable, so if a player is claimed, the player's club has the option to either withdraw the waiver request and retain the player, or allow the waiver claim to stand. The player's club has 48 hours to make this decision, and during this "window" the club has the right to trade the player to the claiming club (but ONLY to the claiming club). If a trade cannot be worked-out with the claiming club before the window closes, and the club chooses not to withdraw the waiver request, the player is automatically assigned to the claiming club for the $20,000 waiver price ($25,000 for Draft-Excluded and Rule 5 players) and the claiming club assumes 100% of the player's contract. (A player with "no trade" rights can refuse both a waiver claim and a trade assignment, however).
If a player is claimed but not traded and the waiver request is subsequently withdrawn, the player cannot be placed on Trade Assignment Waivers again for at least 30 days from the date the waivers are withdrawn, and if the player is placed on Trade Waivers again before the end of the season, the waivers become irrevocable and cannot be withdrawn. A player who has "no trade" rights (full or partial) cannot be placed on Trade Assignment Waivers a second time before the end of the season unless the player first waives his "no trade" rights.
Trade Assignment Waivers secured on a player on Optional Assignment to the minors or on an MLB Disabled List expire after 72 hours.
If a player on an MLB or minor league Disabled List is placed on Trade Assignment Waivers, he must be either traded or reinstated from the DL within 72 hours after the conclusion of the Claiming Period and/or after waivers have been secured.