It may sometimes occur that in the midst and heat of the game a player loses concentration and makes a mistake such as to prevent him from being able to complete his hand. Or it may be that he plays a tile or claims a tile by mistake. In most cases the offending player must pay the two other participants a fine. The hand is abandoned and the Oya places a 100-Tenbo on the table to his right. A new hand commences without any change of Oya or winds. These cases are called Chombo.
There is one mistake, however, that is not considered a Chombo. It is called Shoohai.
Shoohai: A player discovers that he has too few tiles in his hand. He does not have to pay a fine but he cannot complete his hand. Play continues. A Shoohai player’s only recourse is to play very defensively! Also, he will be unable to claim he is Tenpaiat the end of a hand in which there are no winners.
Types of Chombo
1. Taapai: A player discovers that he has too many tiles in his hand. The hand is abandoned. The Oya places a 100-Tenbo on the table and a new hand commences.
2. Illegal Finishes: A player makes a mistake in going Riichi, Ron or Tsumo. The hand is abandoned and a new hand is started with the same Oya (even if it was the Oya who made the mistake).
A player who is Tenpai with a hidden Yaku, who has not gone Riichi and who has a choice of tiles on which to finish, may choose not to go Ron when one of his possible finishing tiles is discarded because one of the other tiles will improve his score (either because it completes another Yaku, or because it is also a Dora tile etc.). However, if the very next tile to be discarded is one of the other ones that the player who is Tenpai needs, it will be a Chombo if he goes Ron.
- Ron-Chombo: A player goes Ron on any tile that he has previously discarded.
- Pon-Chombo: A player goes Pon, then completes his hand with no Yaku (see Pon).
If the Oya makes a Chombo, he pays the two participating players 4000 each. However, he remains Oya and places a 100-Tenbo to his right on the table.
If one of the other players makes a Chombo he must pay 4,000 to the Oya and 2,000 to the other player.
Note 1: If a player who is Tenpai discovers that he has already discarded one of the tiles that he now needs to complete his hand he can avoid a Chombo by not going Riichi. In this case he may go Tsumo even if he finishes with a similar tile to the one he discarded.
Note 2: With Kokushimuso, Shosuushi, Tsuuiisoo, it would also be a Chombo to go Ron on Pei (North Wind) if the player has already exposed one or more Pei tiles as Dora. This is a Chombo even if he finishes his hand by Tsumo. The hand should be abandoned as soon as the player notices the mistake. There is no need to admit to a Chombo unless the player has gone Riichi; the hand can changed to some other combination…
Pei, or the North Wind