Major league waivers are necessary for any player assignment between major league clubs made from August 1 until the day after the close of the regular season. Waivers are not needed for major league assignments during the rest of the year. The trading deadline in which waivers are not needed is July 31. Special waivers are irrevocable. The are required for a major league club to outright a player to a minor league club from September 1 until the 30th day of the following season.
Outright waivers are irrevocable.
They are required for a major league club to outright a player to a mnor league club from the 31st day of the regular season until August 31. Unconditional release waivers can be secured at any point during the year.