CHANGING AN EXPOSURE (Article 6)

Commentary:  When a player calls a discard to make an exposure, they must use the discard if they placed it on the flat part of the rack or if they exposed tiles from their hand. They can change the current exposure (e.g., pung to kong, kong to pung; joker usage; newly exposed tiles) if they have not done a joker exchange (NMJL bulletin 2025; not in MJME) or discarded. A player may also change the number AND type of tiles displayed in the exposure, which ends their turn (in 20 bulletins; not in MJME).

If a player mistakenly picks up the wrong discard and places it on the flat part of the rack, they should be disqualified. Per the 2025 NMJL bulletin, “When you play mah jongg, you must look and listen. A player should never pick up the incorrect title. The player’s hand is dead.”

Per Mah Jongg Made Easy 2024, page 16 #3, “When a discard is misnamed, and another player makes an exposure with incorrect tiles for the actual exposure, they cannot change it. In this case, they should be disqualified.”

Per the league, “If a player mistakenly exposes more than one Pung, Kong, Quint, or Sextet when a tile is called, the hand is now considered dead.” This is a mah jongg in error ruling because when players think they have a winning hand, they prematurely expose more tiles than the current exposure.

Question from a player: A player accidentally exposed the wrong tiles after they claimed a discard. Can they put the tiles back and expose the right tiles from their rack?

Answer from the league: A player may change the number and type of tiles displayed in the exposure until the player has discarded, which ends their turn. Exception: If a player accidentally exposes more than one pung, kong, quint, or sextet when a tile is called, the hand is now considered dead.

Source: Mah Jongg Made Easy (2024 page 15 paragraph 2); NMJL Bulletin 2025

Other answers from the league: 

“As long as the discarded tile was not placed on or in the caller’s rack, it may be returned to the table and the game rules, with the caller now picking a tile from the wall in the center of the board.”

“If a player calls and exposes a pung or kong, she may add to it or take away from it (upon second thought) provided she has not discarded.” 
 
“This player can make any changes to her exposure, as long as it is still her turn.   It is still her turn until she discards, at which point no changes to the before mentioned exposure may be made.” 
 
“You may add to the exposure or take away from the exposure as long as you have not discarded as yet.  Once you discard, you are committed to that exposure.” 
 
“Just as long as she has not discarded as yet, she may change her exposure by adding a tile or taking one away.  Once you discard, you cannot change that exposure.” 
 
“When a player calls for a discarded tile, makes an exposure of a pung, kong, or quint, that player cannot then decide that she does not want to make the exposure.  The player has made the play by call and can only add to or take away from an exposure as long as she has not discarded.”

 “Once a tile has been called for exposure and the exposure is put on top of the rack, the player may add to the exposure or take away from the exposure as long as the player has not discarded.  But the player cannot decide that she did not want the tile she called for exposure, put the discard back on the table and the other tiles into her rack.  A call for a tile is just like a pick from the wall.  Once taken, it cannot be put back.” 
 
Source for other answers:  National Mah Jongg League Bulletin (1970 page 5, 1972 page 5, 1975 page 4, 1977 page 3, 1978 page 3, 1979 page 3, 1981 page 5, 1984, 1987 page 4, 1988 page 5, 1990  page 5, 1994 page 5, 1995 page 4,  1998 page 5, 2003, 2007, 2008, 2009, 2016, 2017, 2019)