Payout for the Player Who Discarded the Winning Tile (Article ID 97)
Abstract: Discarding the winning tile is not considered a penalty regardless of how many exposures the winning player has on their rack. It is not recommended however, that a player throw an obvious tile needed to give a player mah jongg. The person who discard the tile pays the winner double the value and all others pay the value.
Question from a player: What is the penalty for discarding the winning tile? What is the penalty to the discarder when a player has two exposures on their rack?
Answer from the NMJL: “It is not a penalty but a different ruling, that the discarder of the mah jongg tile pays double the value of the hand to the winner. It was not considered a penalty when East paid or received the value of the hand.”
Source: Mah Jongg Made Easy (2020 page 18, Defensive Playing; page 26, Standard Scoring
Other answers from the NMJL:
“It is not a penalty but a different ruling, that the discarder of the mah jongg tile of the hand to the winner. It was not considered a penalty when East paid or received double the value of the hand.”
Source for other answers: National Mah Jongg League Bulletin Q&A 1971, pg 5 https://www.nationalmahjonggleague.org