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.

Invalid win

Players cannot declare a win with an incomplete hand or incorrect waiting tile.

Noten riichi

Riichi must be declared with a tenpai hand. Therefore, riichi declared with a noten hand is penalized.

Unrevealed riichi

If the hand ends in ryuukyoku while at least one player declared riichi, it is a requirement to show the hand as proof of being in tenpai. Depending on the specific rules, a player may refuse to show the hand and instead take the penalty.

Win with no yaku

A hand must have at least one yaku minimum to win. Therefore, declaring a win on a hand without yaku is penalized.

Win during furiten

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.

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.

Wall destruction

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