Generally, an MLB club can trade a player on its MLB Reserve List (40-man roster) and minor league reserve lists at any time. However, there are a few restrictions:
1. A player who was signed after being selected in the First-Year Player Draft (MLB Rule 4 Draft) cannot be traded any earlier than the first anniversary of signing his first contract with an MLB organization.
2. A minor league player eligible for selection in the Rule 5 Draft cannot be added to an MLB Reserve List (40-man roster), traded to another organization, or transferred from one minor league reserve list to another within the same organization, starting with the filing of MLB & minor league reserve lists on November 20th (or November 19th if November 20th falls on a Saturday or November 18th if November 20th falls on a Sunday) and the completion of the Rule 5 Draft.
3. A player cannot be traded while he is on waivers.
4. A player on an MLB Reserve List (40-man roster) who has accrued at least ten years of MLB Service Time with at least the last five years of MLB Service Time accrued with the same club has an automatic "no trade" right for as long as he remains with that club. The player can waive this right if he so chooses.
5. An MLB Article XX-B free-agent who signs a Major League contract after 11:59 PM (Eastern) on the 5th day following the conclusion of the World Series has an automatic "no trade" right through June 15th. The player can waive this right, but if he does he can be traded only for cash and/or player contracts with a maximum aggregate value of $50,000. NOTE: An Article XX-B MLB free-agent who signs a minor league contract after 11:59 PM (Eastern) on the 5th day following the conclusion of the World Series does NOT receive an automatic "no trade" right, even if the player is later added to the club's MLB Reserve List (40-man roster).
6. If a "Player to Be Named Later" (PTBNL) is part of a trade, the PTBNL cannot be on an MLB 25-man roster (MLB Active List) at any time starting when the trade is executed up until the PTBNL is announced. Clubs have six months to agree on a PTBNL. A cash payment (typically $50,000 for trades involving players on the 40-man roster) can be substituted for a PTBNL if no agreement can be reached within six months.
7. Beginning at 4 PM (Eastern) on July 31st and extending through the conclusion of the MLB regular season, Trade Assignment Waivers must be secured before a player on an MLB 40-man roster (or 60-day DL) can be traded.
8. In most cases a player on a disabled list can be traded, even if the player is not eligible to be reinstated and/or healthy enough to play. The one exception is if Trade Assignment Waivers must be secured before the player can be traded. In that case (only), the player must be eligible to be reinstated from the Disabled List AND healthy enough to play before the player can be placed on waivers. Otherwise the disabled player would have to remain a "Player to Be Named Later" until either the player is eligible to be reinstated from the Disabled List AND healthy enough to play such that Trade Assignment Waivers can be secured, or until the conclusion of the MLB regular season (if Trade Assignment Waivers are not secured).