This occurs when someone declares Hu but his/her hand is found to be either (i) incomplete, (ii) lacking the requisite number of tiles, (iii) does not satisfy the agreements about hand patterns made at the start of the game or (iv) does not satisfy the agreed minimum number of Doubles.  In such a situation, the offender loses the agreed Zhi Mo limit points to every other player.

This occurs when a player has too few tiles (i.e. less than 13, 10, 7, 4, 1 concealed).  Such a player is permitted to Kong but cannot Hu.  If he/she declares Hu, it is considered as Zha Hu.

This occurs when a player has too many tiles (i.e. more than 13, 10, 7, 4, 1 concealed).  Such a player is not permitted to Kong or Hu, if he/she declares Kong or Hu, it will be considered as Zha Hu.  

Also, he/she will Bao if he/she discards the winning tile for any player.

When A is said to be Bao by B in the course of a hand, it means that A will bear everyone’s losses in the event that B wins via (i) A throwing the winning tile or (ii) B Zhi Mo the winning tile.  It is usually polite to alert the others to a Bao situation.

There are various ways a person can be ‘Bao’ in the course of the game:

• B has exposed Pongs of 2 of the 3 Dragons.  A throws the 3rd Dragon which allows B to either Pong or Hu (depending on agreed rules).

• B has exposed Pongs of 3 of the 4 Winds.  A throws the 4th Wind which allows B to either Pong or Hu (depending on agreed rules).

• B has exposed Pongs of all honours. A throws an honour tile for B to Pong, Kong or Hu.

• B has exposed 3 Pongs of 1s and 9s.  A throws a 1 or 9 which allows B to either Pong or Hu.

• B has 1 (occasionally 2) Double(s) less than the agreed limit exposed.  A throws a tile that gives B the limit-going Double(s), which B claims via a Pong or Hu.

• B has 9 exposed tiles in one suit.  A throws a tile of that suit for B to Chi, Pong, Kong or Hu.

• B has 9 exposed tiles for Jade Hand or Blue Hand. A throws a tile of that hand for B to Chi, Pong, Kong or Hu.

• B has 7 flowers on the table.  A gets the last flower.

 There are some variations of Bao.  First, Bao can occur even when a player has the maximum number of doubles exposed.  Second, the Bao can be rolled over, i.e. someone can take over being Bao.  Third, if there is a Bao, only the person who Bao, player A, and the person who threw the winning tile, player C, have to pay the winner, player B (i.e. they each foot half the amount of points that the last player D would have lost on top of what ever points they lose).

There are 8 (or 5, in some versions) tiles left to draw in the wall.  A makes a fresh discard (i.e. a tile not in the discard pile) that results in B winning.  A bears the cost of the Hu for all other players.

There are 5 tiles left to draw in the wall.  A makes a fresh discard (i.e. a tile not in the discard pile) that results in B making a Kong.  A bears the cost of the Kong for all other players.

A player cannot claim the second discard of a similar tile to make a Pong or Hu within the same round of discards (i.e. before having a chance to draw).  For example, North has 2 Red Dragons, East discards Red Dragon, South immediately follows by discarding Red Dragon, North then makes a Pong, this is NOT allowed. 

A player cannot make an exposed Pong and then discard the same tile (i.e. forgoing a kong) immediately after claiming the discard.

Also, a player cannot make an exposed Chi by claiming a discard and then discarding a tile that could have been a part of the recently exposed sequence (e.g. a player claims the discard of 4 Bamboo to make an exposed Chi of 4, 5, 6 Bamboo, he/she cannot immediately discard 4 or 7 Bamboo).