Chombo

Chombo is a penalty for heavy rule violations.

Some moves may be considered minor and correctable, like accidentally drawing the wrong tile from the wall. Rule violations subject to chombo are harsh enough to abort the hand and impose a point loss on the offender.

Consequences

A player penalized with chombo must pay a mangan-sized penalty. To each other player, the offender must pay what the offender would have received on a mangan tsumo without honba. An offending dealer must pay 4,000 to everyone, offending non-dealers must pay 2,000 to each non-dealer and 4,000 to the dealer.

The current hand is then aborted and repeated. Players who have declared riichi during the aborted hand get their riichi bet back. Most rules leave the honba count unchanged for the repeat, some rules may handle this like any other abortive draw.

Causes

These scenarios are heavy rule violations and are penalized with a chombo.

Cheating

Cheating is very possible in the game. There are known various and elaborate cheating tricks. Among these include stealing from the discard pile, or tile trading from the hand to the wall. For example, some tricks involve the sleight of hand.

Tournament judges might decide on an even more severe punishment than chombo or disqualify the cheater.

Invalid win

Players cannot declare a win with an incomplete hand or on an incorrect waiting tile. The following conditions are deemed as invalid win:

• The hand must have at least one yaku minimum to win. Therefore, declaring a win on a hand without yaku is penalized.
• A player in furiten cannot win by ron. Instead, by the rule of furiten, a player is limited to winning via tsumo. Declaring ron while furiten is penalized.
• Declaring agari (ron or tsumo) with a noten hand is definitely subject to chombo.

Noten riichi

Riichi may only be declared with a tenpai hand. Declaring riichi with a noten hand is not detected by the other players immediately. It goes unpunished if another player wins the hand or on an abortive draw. The noten riichi is punished with chombo if the player declares a win, or when the hand must be revealed at ryuukyoku. Of course, a player may have declared riichi; and when the hand results in ryuukyoku, the player may opt to pay the chombo penalty, instead of revealing the hand.

Unrevealed riichi

If the hand ends in ryuukyoku, riichi declarers must show their hands as proof of being in tenpai. Depending on the specific rules, a player may refuse to show the hand and instead take the penalty.

Invalid ankan

During riichi, a player may call kan with an ankan, or closed kan. However, this is invalid when the player's wait changes or the three concealed tiles could have been interpreted as something else than an ankou. Other players cannot detect this rules violation immediately, and it is punished at the same time as a noten riichi.

Calling with a dead hand

A player with a dead hand is forbidden to make any type of call, such as chii, pon, kan, riichi, tsumo, or ron.

Wall destruction

A player may not crash and destroy the wall, such that the tile arrangement cannot be recovered.