Restrictions on Trading Players

Technically, a baseball trade is called a Trade Assignment (similar in kind to an Optional Assignment or Outright Assignment). 

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 trade involving a player signed to an MLB contract (including any player on an MLB Reserve List, MLB 60-day Injured List, or MLB Restricted List, and/or any player who was outrighted to the minors after signing an MLB contract for that season) is prohibited beginning at 4 PM (Eastern) on July 31st (or 4 PM Eastern on Friday July 30th if July 31st falls on a Saturday, or 4 PM Eastern on Monday August 1st if July 31st falls on a Sunday) and extending until the day after the final game of the World Series.  
NOTE-1: Beginning with the 2022 season, the MLB Commissioner has the authority to establish the MLB Trade Deadline on any day over the seven-day period July 28 - August 3. However, the MLB Trade Deadline cannot be on the same day as the MLB Rule 4 Draft (First Year Player Draft) signing deadline. 
NOTE-2: Trade Assignment Waivers (which permitted the trading of players on MLB reserve lists after the July 31st deadline up until 12 PM Eastern on the 7th day prior to the originally-scheduled conclusion of the MLB regular season) were eliminated starting with the 2019 season. 

PLAYERS OUTRIGHTED TO MINORS AFTER SIGNING 2023 MLB CONTRACT: (updated 9-12-2023)
David Bote, INF
Chris Clarke, RHP
Shane Greene, RHP
Edwin Rios, 1B 

2. A trade involving a player on a minor league reserve list who is not an outrighted player is prohibited beginning at 12 PM (Eastern) on the 7th day prior to the originally-scheduled conclusion of the MLB regular season through the last day of the MLB regular season (including a day on which a regular season game is played after the originally-scheduled conclusion of the MLB regular season).   

3. A player who signs after being selected in the MLB Rule 4 Draft (First-Year Player Draft) cannot be traded until after the conclusion of the World Series (no earlier than 9 AM on the day after the final game of the World Series), or for 90 days if the player signs after the World Series.   

4. 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, beginning with the filing of MLB & minor league reserve lists in November and extending through the completion of the Rule 5 Draft.

5. A player cannot be traded while he is on waivers.

6. A player on an MLB Reserve List (40-man roster) who has a contractual "no trade" right can waive this right if he so chooses.

PLAYERS ON CUBS MLB RESERVE LIST WITH CONTRACTUAL "NO-TRADE" RIGHT: (updated 5-25-2023)
Ian Happ, OF (full)
Seiya Suzuki, OF (full) 
Dansby Swanson, INF (full) 
Jameson Taillon, RHP (partial)

7. 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 (a so-called "10/5" player) 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.

"10/5" PLAYERS ON CUBS MLB RESERVE LIST: (updated 11-14-2022)
NONE AT THIS TIME

8. An Article XX-B MLB free-agent who signs a Major League contract after 11:59 PM (Eastern) on the 5th day after the final game 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. N
NOTE: An Article XX-B MLB free-agent who signs a minor league contract after 11:59 PM (Eastern) on the 5th day after the final game 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).  

POST-2023 ARTICLE XX-B MLB PLAYERS ON CUBS MLB RESERVE LIST: (updated 6-16-2023)
TBD

9. If a "Player to Be Named Later" (PTBNL) is part of a trade, the PTBNL cannot be on an MLB Active List at any time beginning when the trade is executed (filed with the MLB office) up until when the trade is completed. A PTBNL can be either a specific player or the PTBNL can be selected from a list of players or a class of players as determined by the clubs (in writing) when the trade is executed. 
NOTE: A player signed after being selected in the MLB Rule 4 Draft (First-Year Player Draft) cannot be a PTBNL in any trade made prior to the conclusion of the World Series. Clubs have six months to agree on a PTBNL, but the clubs can agree (when the trade is executed) on a deadline that is less than six months. 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, but the alternative cash payment must be agreeable to both clubs and stated in writing when the trade is executed. 

10. A player on an MLB or minor league injured list can be traded, even if the player is not eligible to be reinstated and/or healthy enough to play.
NOTE: As far as a player having to spend a certain number of days on an IL before he is eligible to be reinstated is concerned, in the case of a trade, time already spent on an injured list is carried-over to the player's new club. 

11. If a player is acquired in a trade and is optioned to the minors by his new club within 24 hours, the player can be recalled from the Optional Assignment at any time without restriction (so that the "ten-day rule" for position players and the "15-day rule" for pitchers & two-way players as it pertains to the minimum number of days a player must spend on optional assignment before he can be recalled would not apply).