CHANGING AN EXPOSURE (Article 6)

Commentary: When a player claims a discard to make an exposure, they are committed to using that discard once it has been placed on the flat part of the rack or once tiles from their hand have been exposed. Within that same turn, the player may adjust the exposure—such as changing a pung to a kong or vice-versa, adding or removing jokers, or modifying the tile count—provided they have not completed a joker exchange (NMJL Bulletin 2025, not reflected in MJME) and have not yet discarded.

The National Mah Jongg League has stated, in various bulletins, that “a player may change the number and type of tiles displayed in the exposure until the player has discarded, which ends their turn,” and in response to a player inquiry confirmed that a player may “add to or take away from the exposure” before discarding. Because the League did not limit these changes to quantity or natural/joker mix, the most literal reading is that a full correction is permitted: a player may remove the incorrect tiles and replace them with the correct ones—even if they are a different suit, wind, or dragon—so long as the discard that was claimed is used in the exposure. Until the NMJL provides a narrower written clarification, this broad interpretation aligns with the League’s published language.

A separate situation arises when a player picks up the wrong discard. According to the 2025 NMJL bulletin, “When you play mah jongg, you must look and listen. A player should never pick up the incorrect tile. The player’s hand is dead.” This is a mah jongg-in-error ruling: using the wrong tile ends the hand immediately.

Another disqualification occurs when a player exposes more than one pung, kong, quint, or sextet when calling a discard. The League states that if a player accidentally exposes beyond the required tiles for the claim, the player can be disqualified. This typically happens when a player believes they have mah jongg and prematurely exposes additional tiles beyond 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: Once an exposure has been made, a player may add to or take away from the exposure up until the time the player has discarded (MJME 2024).

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 (NMJL Bulletin 2025).

Source: Mah Jongg Made Easy (2024, page 1,5 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)