JOKER EXCHANGES ARE OPTIONAL (Article 62)

Commentary: When a player has a natural tile that can be used for a joker exchange, it is their prerogative to make the exchange or not. When to do a joker exchange is situational. For example, consider doing the exchange if:

• The exchange will improve the potential to win
• The exchange will block another player from doing an exchange later
• The exchange will likely not result in the player winning with a pure hand because they have other exposure(s) with jokers
• The exchange will allow a player to discard the joker instead of discarding the natural tile that could be the winning tile for another player

Each of these would apply if you were playing with or without money.

If a player overlooks an opportunity for an exchange or chooses to forego an exchange, it is considered good sportsmanship to not call attention to the situation.

Question from a player:  If I have a symbol tile that can be exchanged for a joker, am I obligated to do the exchange? 
 
Answer from the NMJL:  Joker or Jokers may be replaced in any exposure with a like symbol tile or tiles by any player, whether picked from the wall or taken from player’s hand when it is the player’s turn, however, you do not have to exchange a Joker. 

Source:  Mah Jongg Made Easy (2024 page 23 #1)

Other answers from the NMJL: 

 “Joker or Jokers may be replaced in any exposure with a like symbol tile or tiles by any player, whether picked from the wall or in a player’s hand, when it is the player’s turn, however, you do not have to exchange a Joker.”

“A symbol tile must not necessarily be exchanged for a joker if player wishes to try to go mah jongg without a joker or does not wish to take the chance of their opponent going mah jongg without a joker.”  
 
Source for other answers: Mah Jongg Made Easy (2020 page 22 #3); National Mah Jongg League Bulletin Q&A (1969 page 4, 1971 page 5, 1998)